All language subtitles for AyaSofia Hagia Sophia Saint Sophia. Artistic Treasure, Cathedral, Mosque. S-T- DEUTSCH, ENGLISH

For almost 1500 years, the magnificent silhouette of Hagia Sophia
has towered above the old town of Istanbul,…

…the legendary Constantinople,
the gateway between Europe and Asia.

Hagia Sophia, built in the 6th century,
is one of the most imposing monuments of all times.

Its 56–meter–high dome pushes the boundaries
of gravity, and defies the ravages of time.

The minarets characterize it
as an Islamic religious building,…

…but it was initially built as a Christian church,
about a century before the emergence of Islam.

More than 1000 years lie between its construction
and that of the other mosques in Istanbul,…

...to which it served as a model.

The interior dimensions
resemble that of a cathedral.

The walls are decorated with masterpieces
of Byzantine mosaic art,…

...as well as precious
islamic calligraphy.

The name "Hagia Sophia",
in German "Sophienkirche",…

…comes from the Greek,
and means "Holy Wisdom".

Hagia Sophia is now a museum,
with a very special story.
[Became a mosque again, since 2020]

It is visited every year
by millions of people, from all over the world.

Hagia Sophia was a cathedral for the Orthodox
and the Roman Catholic Christians.
Then was a mosque,...

...and finally a symbol
of the secular Turkish Republic.
[Became a mosque again, since 2020]

In any case,
it is great architecture.

It borders on a miracle
that this unique building still stands today.

Istanbul is located
on an active seismic fault zone.

Throughout its history,
Hagia Sophia has experienced numerous earthquakes.

But, is she really
as sturdy as it seems?

If an earthquake should strike in the future,
it could seriously damage the building.

A major restoration campaign
is currently being carried out.

A team of architects,
seismologists, and engineers,…

...intends to find the weak points
of the structure, so as to prevent its failure.

The Hagia Sophia is still today
a monument of great symbolic value.

Its walls embody the eventful history
of two world religions,…

...and maybe they haven't yet revealed
all the treasures they contain.

Robert Ousterhout teaches art history
at the University of Pennsylvania.

For the specialist
in Byzantine monumental architecture,…

…Hagia Sophia is characterized
by its originality and size.

Hagia Sophia's design was intended to be unique,
and it has remained so to this day.

No experienced builder would ever have dared
to undertake something like that.

The architecture itself was absolutely new,
also in terms of size.

Nothing remotely comparable
had ever been built before.

1500 years later, this architecture
casts a spell, just like on its first day.

The beauty of Hagia Sophia is also,
that today we can experience the interior
exactly like the Byzantine viewer in the 6th century.

We experience
the weightlessness of the building.

We experience the dome
as if it floated on a circle of light.

This interior conveys an experience
that is truly unique in the world.

How long will this experience
still be granted to the visitors?

Since the 6th century, the maintenance
of a building of this size was a serious problem.

Hagia Sophia caused most of the time
high expenses, which at times even led
to it not being fully used.

Today, new spectacular efforts
are being undertaken to preserve the building.

In order to consolidate the masonry,
and restore the walls to their former glory,...

…the largest scaffolding in the history
of Hagia Sophia was erected.

The question is: "Can the monument still resist
the earthquakes that regularly occur in this region?

In 1999, a 7.6 magnitude earthquake struck Istanbul.
Hundreds of buildings collapsed,
and almost 1000 people died.

Experts reckon that another major earthquake
is probable within the newt 20 years.

Eser Çakti, Director of the Seismic Laboratory
at the Bosphorus University,…

...has been commissioned to assess the condition
of the monument, and its resistance to earthquakes.

She explains to her students the special behavior
of the building, and the damage that has occurred.

No matter how important they may be,
the deformations are not Eser Çakti's main worry,…

...but the behavior
of the main structure.

The giant dome and the supporting arches
are under the strictest surveillance.

Sensors for seismographic monitoring
have been installed since about 20 years.

They measure the vibrations,
around the clock.

The data that we receive here
are of great importance.

They provide insight into the behavior
of this gigantic structure.

The data is transferred in real time
to the Earthquake Station at the Bosphorus University.

Here we receive the data
from several dozens of measuring devices...

...that are installed in the most important
historic buildings of Istanbul.

Alone in Hagia Sophia
there are 9 such devices.

A measuring station
is mounted on the floor.

Four are located at the top
of the main supports of the dome,…

...and four more
sit at the top of the arches.

Thus it was found that, during tremors,
some parts wobble dangerously.

Our monitoring shows 2 locations
with especially large vibrations,…

...at the apex of the two main arches
on the east and west sides.

In addition, something seems suspicious
at the southwest pillar.

These vibrations could indicate
potential weak points in the structure.

Even though the building suffered no visible damage
during the 1999 earthquake,...

...that doesn't mean very much
about its seismic safety.

Building behavior is so complex that Eser Çakti
has opted for an unusual approach,
in order to identify the vulnerabilities.

She reduced the building
to its essential structural elements,...

...and a team of engineers built on that basis
a model of brick and mortar.

This model will be subjected to an earthquake simulation
on top of a special vibrating platform in the laboratory.

The same team already carried out a similar experiment
with a model of a mosque in Macedonia.

The gigantic dimensions of Hagia Sophia
are a real challenge for engineers.

This project confronts us
with difficult tasks.

On the one hand,
the construction of the arches.

On the other hand,
that of the domes.

And third, the assembly
of the individual elements,...

...because the model has to behave
like a unified structure.

Those are, in my opinion,
the 3 critical points.

If the architects of Hagia Sophia, in the 6th century,
dared to erect such a gigantic building,…

...it was – no doubt – because they wanted
to convey a message to the whole world: ...

...the announcement
of an important event in human history.

In the 3rd century, the Roman Empire ruled
over the Mediterranean,…

...but keeping it under control
was very difficult.

Emperor Constantine the Great
therefore founded a second capital,…

…– Nova Roma, “the New Rome” –,…

...on the territory of a former Greek colony
on the shores of the Bosphorus: …

…BYZANTIUM.

Soon the city was called Constantinople,
"the City of Constantine",…

…and that Roman emperor,
who was well-disposed toward Christianity...

...built a basilica
dedicated to the Holy Wisdom.

A century later, Christianity had become
the state religion of the Roman Empire.

But then the Empire was split in two: …

…Western Rome, with Ravenna as its capital,…

…and Eastern Rome,
with its capital in Constantinople.

In the course of the 5th century,
the Western Roman Empire collapsed...

…under the pressure
of the barbarian tribes.

The Eastern Roman Empire,
henceforth called Byzance,...

…experienced in the 6th century,
under Emperor Justinian, a decisive revival.

Justinian saw himself
as the heir of the Roman Empire,…

...and as God's representative on earth.

But Constantinople
resisted his ambition.

No sooner had Justinian ascended the throne,
his authority was already being questioned.

The biggest threat, in 532,
was posed by the Nika uprising.

After several days of unrest, Justinian
feigned to meet the demands of the rebels.

But, when they gathered
in the Hippodrome,…

...he let the gates be closed, and his soldiers
slaughtered the rebels by the thousands.

Justinian consolidated his power.

From then on, his main concern was
rebuilding the city,…

…because, during the Nika uprising,
many buildings,…

…including the previous one of Hagia Sophia,
had been destroyed.

Justinian turned Constantinople
into the largest city in the then known world.

And, to affirm his power,
he desired to build a monumental basilica.

But what shape
would be appropriate for a building…?

…that was to proclaim to the whole world
the birth of the first great Christian Empire?

Joan Branham teaches art history
at Providence College in the USA.

Her specialty is the development
of religious architecture in early Christian times.

In Ravenna, she visits the Church of San Giovanni,
whose construction plan dates back to the 4th century.

In the 4th century,
Christianity was officially legitimized,…

…and suddenly, large imperial funds
became available for building churches.

But the question was…

…"What should be the arrangement
of the sacred space of the early Christian community?

Greek and Roman temples
were reserved for the gods and the priests.

The believers had no access to them.

The Christians decided to gather
their assemblies in closed rooms.

Therefore, they took as a model
a type of Roman building…

…that was used
for Justice Court sessions: …

…the Basilica.

The early Christian basilica
is a large, mostly rectangular room.

It consists of a central nave,
with possibly one or two side aisles.

On one of the narrow sides is
a semi–circular bulge,…

...the so-called "apse".

It includes the altar,
about which the priests officiates.

For his Holy Wisdom church,
Justinian chose the rectangular plan,…

…which would, from now on,
become associated with the Christian faith.

At the same time, the building
was to symbolize Justinian's imperial power.

Another Roman architectural model
had already been used for that purpose: …

…the dome of the Pantheon,
which embodied the power of Rome for centuries.

Justinian wanted to implement
a completely new concept,…

…by merging the imperial
and the religious power.

In order to give shape to his vision,…

…he appointed a brilliant mathematician,
Anthemios of Tralleis…

…and a geometer, Isidore of Miletus.

Both came
from the Platonic Academy of Athens.

Anthemios of Tralleis
and Isidore of Miletus were scholars.

If someone asked me to design a building,
they would get themselves into a lot of trouble.

I am a university professor,
not a trained architect.

Justinian trusted the two men with
100 builders, 10,000 workers, and an unlimited budget.

The two scholars let themselves
into a completely new experiment.

Even an experienced architect
wouldn't have dared,…

…because no element of Hagia Sophia's structure
was based on experience: everything was absolutely new.

The basic idea was the dome,…

…which covers a central square of 100 by 100
Byzantine feet – about 30 meters –,…

...on which lies the dome,
100 Byzantine feet in diameter.

This basic shape is extended East and West
by two 15–meter half–domes.

The design of Hagia Sophia is pure geometry;
it is pure mathematical poetry.

An experienced architect would never
have thought of such a bold design.

The first question raised
by this geometric abstraction, is: ...

"How should such a large dome
be supported?"

The solution was: a structure made up
of 4 Romanesque arches of extraordinary size.

There are no arches, anywhere,
with the same span as at Hagia Sophia.

The largest extant Romanesque arch
measures perhaps 50 Byzantine feet.

The arches of Hagia Sophia
measure 100 Byzantine feet.

This was a first
in Romanesque architecture.

How can one ensure
that such an arch does not collapse?

The construction of a model confronts Esher Çakti
and her assistants with a similar problem.

Like the builders of Hagia Sophia,
Çakti's team also uses a wooden framework,…

…above which the arch
of brick and mortar is built.

The capstone is the key element;
it completes the arc.

Once it is in place,
both halves of the arch are connected,…

…and the compressive force on the ground
can be discharged on both sides.

A giant dome
has a huge weight.

Also in the model.

What weight can the arches carry?

To find this out, Esher Çakti installs
measuring devices at the tops of the arches,…

…similar to those attached
on Hagia Sophia 's arches.

They measure the deformations
as a function of the loads.

Here, sandbags are used
to simulate the weight of the dome.

Each sack weighs 25 kilos.

According to the computer calculations,
each arch in the model should withstand about 15 sacks,…

…before the deformation
leads to its collapse.

But already with the 5th sack…

No one is injured, but the arch
collapsed under little more than 100 kilos.

The reduction in model size
sometimes causes surprises.

But that's all part of the experiment,
and it is very insightful for Esher Çakti.

It's always interesting
to see the collapse up close.

The work on the computer
gives just a general idea of how it happens,…

…but only
in a real test of this kind,…

…or in the case of a real earthquake,
of course,…

…we can see in detail
how the structure collapses.

In slow motion, the lateral pressure due to the weight
of the sand sacks can be clearly observed,…

…until the deformation of the arch
eventually results in its collapse.

The central dome of Hagia Sophia
also exerts such a side thrust.

To counteract it,
Anthemios and Isidore have.

…added supports to the arches on the outside
of the building, in the east–west direction,…

…by means of buttresses
running over the aisles.

For the north–south axis, they chose
another solution, namely "half–domes".

The two half–domes
have the same function as the buttresses: …

…they increase
the load–carrying capacity of the arches.

This architectural innovation also allows
the expansion of the inner space,…

…and so, to obtain
a very large free volume.

The great dome vault
offers the visitor a spectacular sight.

But one last problem
was still to be solved: ...

…the transition from the square floor plan
of the arch construction to the round dome.

Four spherical triangles
– so-called “pendentives” –,…

…which are inserted in the corners between the arches,
carry out the harmonious transition.

Neither the arches, nor the pendentives,
were applied here for the first time.

What was new, however,
was the scale of construction.

Justinian's wish was fulfilled.

The extraordinary dome,
at the same time sublime and airy,…

…rises above the rectangular room
of a Christian basilica of unprecedented proportions.

In addition, this monumental structure
was built in a surprisingly short time.

Justinian wished the immediate
and rapid erection of the building.

It was finished
in less than 6 years.

Think of the Gothic cathedrals in France.

Reims Cathedral, with the shortest
construction period of all, took at least 80 years,…

…although it is significantly shorter
and narrower than Hagia Sophia.

The interior was also
up to the architectural ambitions.

Justinian's Hagia Sophia
is a spectacle in stone.

He had marble for his great church
brought from all parts of his empire.

The purple pillars came
from the royal quarries in Egypt.

The porphyry marks
the imperial presence in Hagia Sophia.

Even stone from North Africa
was used.

The tallest pillars
measure over 20 meters.

Their capitals are masterpieces
of lace, carved in stone.

Every ornament contributes
to the symbolic power of the whole.

The building represents
the kingdom of Justinian.

The diversity of the marble is a geographical lesson
on the extent and size of the empire.

And above the whole rises the vault of Heaven,
represented by the gold mosaics.

Mosaics became
the Byzantine art "par excellence".

They experienced, under Justinian,…

…and in connection with the spread
of the Christian faith,…

…and the creation
of numerous basilicas,…

…a lightning development.

The Basilica of San Vitale in Ravenna
was built just a few years after Hagia Sophia.

It is one of the few basilicas in the world
in which so many figurative mosaics
are preserved from the time of Justinian.

Here can be appreciated the significant development
that this art form went through in that epoch,…

…to become a signature, so to speak,
of Byzantine Christianity.

The Romans used mosaics
mainly as floor covering.

The Byzantine artists, on the other hand,
employed mosaics to cover entire walls and ceilings.

If a Byzantine visitor
entered the Church of San Vitale,…

…he must have felt that he had been transported
into a completely different world.

The mosaics were not
just wall decorations,…

…they also served
to spread the Christian faith.

These pictures tell
biblical stories,…

…and contain
theological messages.

The people
who couldn't read the Bible…

…learned its stories
from these pictures.

In Ravenna, far away
from the capital Constantinople,…

…the mosaics
convey also a political message.

In San Vitale,
Emperor Justinian and Empress Theodora…

…appear connected directly
with the biblical scenes.

This new way of using the mosaics
as bearers of imperial and religious messages…

…led to a parallel development
of the applied materials.

In the School of Mosaic Art,
two steps from San Vitale,…

…Luciana Notturni teaches
the techniques and materials of the time.

The so–called "pizza", a sort of glass plate,
is at present produced in Venice.

In earlier times,
this was done directly on the spot.

According to their needs,
the artists broke down the colored glass plates.

The individual cubes or tiles thus obtained,
of different sizes, are called "tesserae".

The colors are special,…

…because natural substances do not provide
any blues, turquoises, or bright reds.

Especially in demand
among Byzantine artists and their clients...

…were silver and golden tesserae.

On a small, transparent pizza,
will a gold foil is first laid on,…

…and then a wafer-thin glass pane,
mouth–blown, is placed on top.

The whole is then heated in the oven
to produce this golden material,…

…which reflects light
in a very special way.

This property is mainly due to the fact
that it really is 24–carat gold.

This material is used in almost all mosaics
where light reflections are desired,…

…because gold is not a colour,
it is simply light.

This symbol of purity corresponded exactly to the message
that Justinian wanted to create with his great church.

Unlike San Vitale,…

…the decoration of Hagia Sophia was intended
to be abstract, conceptual, and of course unique.

The gold mosaics are spread
over an area of 280,000 square meters.

There were motifs of the Cross,
but there was no image of God the Father,…

…none of the Virgin Mary, and none
of the standard characters appearing in later Byzantine churches.

Even in this abstract, pure form,
the message of the mosaics was accessible.

The profusion of gold symbolizes light,…

…because light symbolizes God,…

…whom Byzantine Emperor Justinian
represented on Earth.

In 537, Justinian presented
the Hagia Sophia to the world.

The gigantic building had nearly emptied
the state coffers of the Byzantine Empire,…

…but its intended effect
was fully obtained.

Historical reports tell about it.

It took 5 years to build.

Previously, the land
had been unoccupied,…

…and now, suddenly, this stone giant stands there,
in the middle of Constantinople.

In the centuries to come,
it was called "the Great Church".

For the Byzantine Empire,
who pretended to universal dominance,…

…it was the center of the world.

And, for Justinian, it was a fantastic setting
for displaying his power.

Justinian used Hagia Sophia
as a stage for his imperial ceremonies,…

…because they ensured order
in the well–governed cosmos.

In the Hagia Sophia,
Church and State came together.

For the people
who attended these ceremonies,…

…the grandiose shows
were almost a mystical experience.

Whoever entered Hagia Sophia,…

…must have had the direct impression
that the gates of Heaven were being opened for him.

Hagia Sophia was out of this world:
it was supernatural.

However, this state of grace
didn't last long: …

…on May 7, 558, barely 20 years
after the consecration of the church,…

…a series of earthquakes resulted
in the collapse of Hagia Sophia's dome.

The first dome was a great experiment,
and architecture was, at that time, a matter of trial and error.

As impressive as the dome was,
it wasn't solid enough…

…to withstand the earthquakes
that frequently occur in Constantinople.

The dome was rebuilt
by Isidore the Younger,…

…nephew of the first Isidore,…

…and that one
is still preserved today.

Why did the original dome
collapse after only 20 years,…?

…while the dome that replaced it,
is still standing, 1500 years later?

According to the descriptions available to us,
the old dome looked a little different from the present one.

The original dome was much flatter;
rather a shell, not a truly semi–spherical shape.

It possibly resembled the dome
of Hagia Irene, the Church of St. Irene,…

…which was built
a few years earlier.

This very flat dome
rests on a cylinder with windows all around.

Isidore the Younger then decided
to use a higher, more curved shape.

In effect, this choice
did make the dome more resistant.

A flat dome tends to press sideways
against the supporting pillars.

With a more curved dome,
the pressure is discharged vertically onto the columns.

This principle of construction
is so efficient…

…that Isidore the Younger could
– between the ribs that transmit the load –,…

…provide openings for 40 windows.

That is the reason the dome appears
as weightless as its predecessor.

Hagia Sophia, 56 meter high,
and almost 80 meters long,…

…was, until the construction
of Seville Cathedral,…

…a century later,…

…the largest vaulted room in the world.

However, how would today's building structure
react to an earthquake?

Will it be able
to support the dome?

At the Bosphorus University,
work on the model continues.

Arches and supports
have been rebuilt.

Now the team is erecting
the two additional supporting semi–domes.

The mortar has been drying
for several weeks now,…

…and the wooden framework
can now be taken off.

Suddenly, a big crack!

With these cracks, the dome
will never succeed the seismic test.

In order to examine in more detail
the behavior of the mortar,…

…the masons must take the dome
completely apart.

Just like the construction of Hagia Sophia,
this model is also an experiment.

It is always necessary
to make new attempts.

There are
2 different strengths: …

…on the sides,
the mortar layer is 4 cm thick.

But at the point where the crack occurred
the thickness is only half a centimeter.

The mortar cover has contracted
in the drying process.

We must change
the mortar's properties,…

…or add substances
that will increase its solidity.

In Byzantium,
the collapse of the dome,…

…the symbol of Emperor Justinian's power,
was certainly received much less calmly.

We don't know how Justinian reacted
to the collapse of the dome.

He certainly wasn't happy.

Anthemios and Isidore were at this time
– luckily for them –, already dead.

Ii is an irony of history that, when Hagia Sophia's
dome collapsed, the Eastern Roman,…

…the Byzantine Empire,
also began to crumble.

Justinian had wanted to restore
the once powerful Roman Empire,…

…whose heir he claimed to be.

But, since the second half of the 6th century,
the Empire had lost more and more territories,…

…and it would never again
attain its ancient extension.

In the 7th and 8th centuries, the world
around Christian Byzantium changed significantly.

The west saw the expansion
of the Christian empire of the Carolingians,…

…who also claimed, supported by the Pope,
to be the rightful heirs of Rome.

In the north, the Slavs and Bulgarians
kept Byzantium constantly under pressure.

But the main threat was to the south and east,
where Islam was bent on conquest…

…against Constantinople,
which now became the bulwark of Christendom.

The growing pressure exercised
by the new religion of Islam…

…produced in Byzantine Christianity
a very severe crisis.

In monasteries and churches,
religious images were ardently revered.

This was, however, denounced as idolatry.

And the military failures were seen
as an expression of divine disapproval.

Therefore, the authorities caused
all figurative images to be destroyed and forbidden.

This so–called "Byzantine Iconoclasm" dispute
dragged on for over a century.

The veneration of icons
was not reintroduced until 843.

Hagia Sophia's non–figurative mosaics
could emerge unscathed from this dispute.

And, when it was finished, the embellishment
of the building had a spectacular upswing.

Hagia Sophia was the flagship
of the Byzantine Empire,…

…a sort of advertising space
of dreamlike proportions.

So it became absolutely necessary
to decorate the church with figurative motifs,…

…in order to display the orthodox position
in the spirit of the state religion.

The implementation of figurative mosaics
in a building like Hagia Sophia…

…is a complicated process.

First, the artist
creates a drawing…

…which is transferred to the wall
as a sketch.

He can thus check whether that spot
is suitable for the desired image.

In order to transfer
a drawing to a wall…

…certain rules must be followed.

On a curved surface there is also
a question of perspective and proportions.

Then, a mixture of lime and marble powder is applied,
into which the Tesseræ are inserted.

The size of the wall section
to which the mortar is applied…

…must be such that the specialized mosaicist
can cover it with mosaic in one working day.

These periods were referred to as "giornate",
i.e. day, or day's work, in Italian.

The motif is applied again to the mortar layer,
and also provided with color information.

Now the mosaicist
can start work.

Each tessera is inserted by hand.

The angle of inclination varies,…

…and the irregular surface
causes different light reflections.

Talent and inspiration of the mosaicist
are not only expressed by his interpretation of the motif,…

…but also by the positioning
of the individual stones.

Because of the curvature,
the image is brought to life,…

…and gives the impression of movement.

The positioning of the tesserae
interacts with the incident light.

And thereby with the positioning of the windows,
which were the main light sources.

Today it is hard for us to imagine,…

…how much time and effort have gone into the decoration
of the walls and ceilings of this gigantic structure.

Luciana Notturni has worked on this motif
for about 10 days.

Today it is a long
and costly labor,…

…but it was no different
even then.

Such mosaics
were funded by the Emperor.

Hagia Sophia is much larger
than any other Byzantine church.

Covering these huge areas with mosaics
was a colossal undertaking.

Decorating the dome with a new mosaic
would require an immense scaffold.

The Virgin Mary in the apse
is about 5 meters high,…

…but, within this architecture,
she appears much smaller.

The decoration of this building with figurative representations,
was a complex and time–consuming undertaking.

Since nearly all Emperors
made their contribution over time,…

…the most important masterpieces
of Byzantine art are assembled in Hagia Sophia.

Hagia Sophia is of the highest importance
from the point of view of the history of art,…

…because mosaics were created here
over many centuries.

This building alone provides
a rich panorama of Byzantine mosaic art.

This mosaic was
added in the 10th century,…

…400 years after Justinian's death.

His church, however, was still, as before,
the symbolic center of Christianity.

Although the Empire dwindled politically,
Constantinople nevertheless retained a great prestige,...

…and the legendary capital
was regularly besieged by Muslim armies.

Eventually, however, it was the dispute between
the Church of Byzantium, which became the "Orthodox" Church,…

…and the Catholic Church of Rome,…

…which delivered
the deathblow to the Eastern Empire.

The motives of the dispute between Catholics
and Orthodox are difficult for us to understand today.

Generally speaking,
the dispute was about power.

Who would ultimately
be the head of the Christian Church?

The Pope, in Rome,
or the Patriarch, in Constantinople?

The fourth crusade,
which left Venice in 1204,…

…ended with the capture of Constantinople,
and the founding of the Latin Empire.

For 60 years, the Crusaders plundered
the riches of the former metropolis;…

…among other things, they stole all the gold
of the Hagia Sophia mosaics.

It was reapplied
in the Basilica of San Marco,…

…and symbolizes now
the power of Venice.

When the Byzantines finally succeeded in reconquering power,
Constantinople had been bled dry.

In a last, supreme effort,…

…the Byzantines produced, in the following
2 centuries, their greatest works.

The Chora Church,
in Istanbul's Fatih district,…

…is an outstanding example of this.

But the most poignant testimony of the swan song
of this civilization is located in Hagia Sophia.

The monumental Deesis mosaic,
on the south gallery,…

…is considered
the absolute masterpiece of Byzantine art.

In the mid–15th century,
the Byzantine Empire was limited…

…to the immediate vicinity
of Constantinople, and the Peloponnese.

The Ottoman Empire already had taken possession
of Anatolia and large parts of the Balkans.

Despite all the desperate appeals,
the Christian Western Empire refused to help.

On May 29, 1453,…

…the troops of Sultan Mehmed II
entered Constantinople,…

…and sealed the end of Byzantium.

This also meant the beginning
of a whole new story for Hagia Sophia.

The church is now almost 900 years old,
and still towers proudly over Constantinople.

But, even then,
the building required urgent repairs.

Sonay Sakar is an architect.

She directs the current
restoration campaign.

This maintenance work will have to continue
as long as Hagia Sophia stands.

If the restorations of Hagia Sophia
were eventually stopped,…

…then there would be
cause for great concern.

There have even been attempts at consolidation
which interfered with the stability of the building.

In the 1950s, this wall was reinforced
with quick–setting cement.

Under the influence of wall deformation,
it became brittle.

The cement in the wall is collapsing,…

…and thus significant deformities
appear on the surface.

So the effect of the intervention
was the opposite of the desired one.

In the case of an earthquake,
this wall could collapse.

The cement has to be removed
out of the wall.

The original bricks
are amazingly well preserved,…

…and can be reused.

The cement
is replaced by a mortar,…

…which should avoid
the previous mistake.

When it comes to restoration, our principle is to pay attention
to the use of traditional materials and techniques.

The mortar you see here was developed in the laboratory,
after a careful analysis of the original mortar of Hagia Sophia.

For centuries, legends have claimed
Hagia Sophia owes its resilience…

…to the holy relics,
and fragments of the Cross of Christ,…

…which are embedded into its walls.

The analyses of the mortar in the Istanbul laboratory
have led to a more rational explanation.

An original specimen from the 6th century
was crushed,…

…ground, and shaken,…

…and subjected to a series of tests.

As with most old mortars, here too
the main components are lime and water.

But the mortar of Hagia Sophia
also contains brick fragments.

And THEY seem to be
the key to its resilience.

As you can see in this mortar sample,
it contains brick fragments.

They enter into a special chemical compound
with the lime.

The brick fragments contain
volcanic ash and calcium carbonate.

These elements
form a very solid,…

…but also a very elastic combination
with the classic mortar.

The chemical reaction produces "pozzolanic" mortar,
thus named after a volcanic rock,…

…which contributes significantly
to the great resilience of the building structure.

The pozzolanic mortar is more flexible than the modern one:
it is very elastic, and behaves almost like wood.

If the restorers
use this old mortar compound,…

…they will be doing far more
than repair the building.

They want to make it earthquake–resistant,
as it originally was.

To do this, however, they must consider
another special feature of this building.

Hagia Sophia is different
from the other buildings by the strength of the mortar…

…between the bricks,
which has pozzolanic properties.

Thanks to this property, there is a high adhesive strength
between the bricks and the mortar,…

…which thus move together.

Since both mortar and brick
are comparatively light,…

…the walls are very light
and very elastic.

This combination of flexible mortar and brick
is extremely coherent,…

…and it allows the wall structure to adapt itself
to deformations caused by earthquakes.

The Earthquake Laboratory of the Bosphorus University
thus solved the mortar problems too,…

…and the team could
rebuild the half-dome.

For the central dome, as has been shown,
another solution had to be found.

We have come to the conclusion
that a brick dome was easier to build.

This dome also allows window openings,
similar to those in Hagia Sophia.

So the model now approaches
even more to the original.

Before the test
can be carried out,…

…the 7–ton model
must be transported to the seismic test plate.

This is the largest model
that we have ever built here.

We have to be very careful.

The model must stay
perfectly horizontal,…

…otherwise it may be damaged.

If something happens now,
months of hard work would be wasted.

The structure is so heavy that the iron plate,
on which it rests, yields dangerously.

But finally the model stands on the vibrating table,
without having suffered any visible damage.

The last wooden supports are removed,
and Esher Çakti checks every centimeter for cracks.

We have discovered fine crack
in the half–domes.

But they are only visible from the inside.

But, luckily, these are only superficial cracks,
which do not affect the structure itself.

Next, measuring gauges
placed in the same places…

…where building fluctuations have been recorded
in the Hagia Sophia, for the last 20 years.

We can then record
the vibrations during the experiment,…

…and compare them
with those measured on the Hagia Sophia.

On this basis, conclusions can be drawn
about the behavior of Hagia Sophia
in case of a real earthquake.

The building structure of Hagia Sophia
and its proportions are so extraordinary,…

…that today no one can say what will happen
if one of the main elements fails.

As the Ottomans
took Constantinople…

…they were overwhelmed
by the uniqueness of this symbolic building.

For Mehmed II, Hagia Sophia
was the climax of his conquest.

The conquest of this landmark
was essential to his new kingdom,…

…and his first official act consisted of…

…converting Hagia Sophia into a mosque.

How could this building,
which symbolizes Christianity, become a mosque?

From an architectural point of view, it was not at all difficult
to take the Christian sacred building…

…and transform it
into a Muslim one, into a mosque.

A pulpit, the "Minbar",
was added,…

…and also the "Mihrab", the prayer niche,
that points towards Mecca.

The dome, on the other hand,
symbolizes the heavenly sphere in both religions.

A minaret was erected.

And, from then on, the basilica Hagia Sophia
became the mosque "AyaSofya".

Initially, the Ottomans
changed the building only a little.

Robert Ousterhout sees the reason for this
in the symbol value.

At the beginning of Ottoman rule, Hagia Sophia
was both an active mosque and a symbol of victory.

In order to keep this role of triumphal landmark,
it had to continue to look like a church.

Whoever entered the Hagia Sophia had to realize
that it had once been a church, but was that no more.

That was the intended message.

The will to appropriate the Byzantine heritage
is also reflected in the fact that Mehmed
made Constantinople the capital of his empire.

He also built the Topkapi Palace
near Hagia Sophia,…

…which thus became
the Sultan's own mosque.

Irvin Cemil Schick, from Shehir University
in Istanbul, is convinced…

…that, apart from the symbolic value, the architecture itself
held a great fascination for the Ottomans.

When you look at the mosques
that were built before the conquest of Istanbul,…

…you will see that, architecturally,
they were much less developed.

They have a lot of pillars,
carrying many small domes,…

…and, consequently, their interior
is always comparatively small.

That's why they admired
this completely different building,…

…and they wanted to imitate it.

Like Justinian, 9 centuries before,
Mehmed II also designed…

…an important reconstruction program
for his new capital.

For the future mosques,
the model would be Hagia Sophia.

Several mosques, modeled on Hagia Sophia,
were literally raised from the ground.

The first large mosque based on this model
was the Fatih Mosque, which Mehmed II chose for his tomb,…

…next to the graves
of Justinian and Constantine.

The admiration
for the architecture of Hagia Sophia…

…reached its highest point in the 16th century,
with Mimar Sinan, the official architect of Suleiman I.

Mimar Sinan, known as "Sinan the Architect",
is certainly the most important Ottoman master builder.

It's really seldom in history that someone
is responsible for so many important buildings.

And when I say buildings, that comprises
from bridges, to public baths, to mosques.

He built just everything.

His genius is maybe even comparable
to that of to Michelangelo.

Sinan was deeply impressed
by the formal clarity of Hagia Sophia,
and the architectural boldness of the Byzantine builders.

He was concerned about the deformations
which he noticed on the thousand–year–old building…

…and he strengthened it
by a whole series of new support structures,…

…which give the complex
the massive silhouette that we see today.

Without those measures,
the building would probably have collapsed long ago.

His contribution to Hagia Sophia
was therefore also crucial.

But, apart from that, he designed
numerous mosques and many other buildings.

Istanbul is hardly imaginable
without him.

Throughout his architectural career,
Sinan tried to approach…

…what he considered
an absolute masterpiece.

The Suleiman Mosque,
which he designed for Suleiman I,…

…is in this sense
one of his most successful creations.

Built almost 1000 years
after its model emerged,…

…it is a reaction of Ottoman architecture
to the Byzantine genius,…

…but also an homage to it.

With the Suleiman Mosque, he managed to create a volume
which is as magnificent as that of AyaSofya,…

…and he also succeeded
in giving to the room the same divine meaning.

At the same time, Hagia Sophia, as the Ottoman
Sultan's Mosque, underwent a gradual islamization.

More minarets were added,…

…and on its walls appeared masterpieces
of an Islamic art "par excellence": calligraphy.

The dome was designed by a 19th–century calligrapher,
named Kazasker Mustafa Izzet Efendi.

The text is the "Verse of Light".

It starts with:
"God is the light of heaven and earth".

The verse is not complete.

There was not enough room for it.

The fact that the verse is written doesn't mean
that people should read it from beginning to end.

Rather, the verse protects
the house of prayer and the church.

In that sense, it has indeed
fulfilled its job since that time.

The calligraphy symbolizes, in a
very special way, the Ottoman civilization.

Savas Çevik, one of the most important
contemporary calligraphers of Turkey,…

…teaches this technique in his studio,
on the Asian side of the Bosphorus,…

…transmitting it to his students.

Islamic calligraphy arises
from the obligation of the Muslims,...

…to preserve the Word of God
in the most beautiful forms.

Today, it is
a highly developed art form.

It obeys strict rules,…

...but at the same time it leaves ample room
for variety, and for the creativity of the performers.

It is not mandatory,
but most calligraphers are religious,…

…since most of the texts they write
are religious texts.

There is, therefore, an advantage
if they are believers.

But a friend of mine,
from Iraq, is a Christian,…

…and he's an excellent calligrapher.

…which proves that one doesn't have
to be a Muslim, to do this work.

Finesse and purity of these Ottoman works of art
are generally recognized.

They reach their peak when thei are
an integral element of the architectural composition.

The volume of Hagia Sophia
was a particular challenge,…

…but the Ottoman calligraphers
mastered it with flying colours.

The 8 giant medallions of the AyaSofia
are a material testimony to this.

The calligraphic medallions
have a diameter of 7.5 meters.

This Islamic inscription is probably
the largest in the world.

Someone who enters the building
for the first time…

…might perceive this calligraphy
as an intrusion into the whole.

But for someone who grew up here,
they are a natural part of it.

I myself can't even imagine
Hagia Sophia without them.

Aside from these additions,…

…the decoration of the walls of Hagia Sophia
raised delicate questions.

Several statements and actions of Prophet Mohammed,
which have been handed down,…

…clearly indicate that a house of prayer
should be free of images.

So the Byzantine mosaics
raised a problem of principle.

However, several centuries passed
before religious ordinances…

…won the upper hand
over the admired art works.

The mosaics remained visible, even after
Hagia Sophia had been converted into a mosque.

And the illustrations of the first Western visitors
after the islamic dedication are proof,…

…that they were still there.

The mosaic of the Virgin Mary, in the apse,
remained untouched until the 18th century.

In the 18th century,
Islam took on more conservative traits.

This was the first time that, in Hagia Sophia,
all figurative mosaics were covered.

Thus, all Byzantine masterpieces disappeared
from the walls of Hagia Sophia,…

…and gradually fell into oblivion.

After conquering Constantinople,
the Ottoman Empire soon reached a gigantic extent.

In the 18th century, however,
it began to falter,…

…and a century later its prestige had diminished,
and it had lost large territories.

In 1847, Hagia Sophia was again
severely damaged by earthquakes.

Its pitiful condition resembled
that of the entire Ottoman Empire.

The repair and support measures
were entrusted by Sultan Abdülmecid I…

…to the Swiss architect Gaspare Fossati.

Carlo Agliati manages in Bellinzona, in the Ticino
Cantonal Archive, the documentation left by Fossati.

The mosque was, especially concerning its structure,
in a desolate condition.

There are testimonials
from that time, which attest...

…that the main dome
even had cracks and dislocations,…

…through which an adult man
could have passed.

Fossati reinforced the dome
and restored the wall decoration.

The present colors
of Hagia Sophia's walls,…

…date back to this restoration.

This work even led
to a fantastic discovery.

The most important discoveries of Gaspare Fossati
during the restoration work…

…were the masterful Byzantine mosaics
under the vault of the dome,…

…but also in the Nartex,
and really everywhere in the building,…

…which were uncovered during the removal
of the plaster, made of gypsum or lime.

Having remained intact after the earthquakes
and the Ottoman layers of plaster,…

…the mosaics appeared
in all their glory.

Fossati's main concern was the preservation and documentation
of these important testimonies from Byzantine times.

Fossati had to hurry.

Although he had a written order
of young Sultan Abdülmecid in his pocket,…

...the pressure of the religious movements, especially at a time
of weakness of the Ottoman Empire, was very strong.

At the time, it was much discussed
whether these mosaics should remain visible or not.

The Fossati brothers discovered
that the workers defaced them.

Therefore they decided to make copy drawings
as soon as possible, and then whitewash them again.

The mosaics disappeared again, and Hagia Sophia
looked very much like a mosque again.

The First World War
hastened the end of the Ottoman Empire.

Fighting on the side of the Germans,
the "sick man on the Bosphorus",…

…as the kingdom was also called,
was completely devastated by the war.

In a last nationalist uprising, the soldiers
under General Mustafa Kemal united.

He expelled the Europeans from Anatolia,
and proclaimed the Republic of Turkey in 1923.

That put a final seal
on the fate of the Ottoman Empire,…

…and Hagia Sophia began
the third chapter of its checkered history

The young republic wanted to be secular,
and Mustafa Kemal affirmed this symbolically.

He turned the mosque AyaSofya
into a museum.

Parliament awarded Mustafa Kemal
the title "Atatürk": father of the Turkish People.

That happened on the same day
when the mosque became a museum.

Therefore, the secularization of AyaSofya
became a sort of symbol of the Turkish Republic.

The building was in dire need of repair.

Atatürk commissioned Thomas Whittemore
and the Byzantine Institute of America
with a new restoration campaign.

Now the Byzantine mosaics
discovered by Fossati would also be…

…freed again from the plaster layer
from Ottoman times.

On this occasion, most of the masterpieces
visible today were uncovered, and carefully restored.

Their reappearance increased the interest
in the history of Byzantium,…

…because now the double history
of Hagia Sophia was apparent to everyone.

Above the prayer niche you can see
two large writing medallions,
and in between a wonderful mosaic.

The right medallion says:
"Allah, praise be to his domination".

The left medallion:
"Peace with Mohammed".

Obviously, these words have
the highest symbolic value in Islam.

And, right between the two medallions,…

…there is this wonderful mosaic,
with the Virgin Mary and the baby Jesus.

This connection between Islam and Christianity
is for me the real landmark of Istanbul,…

…yesterday as today.

The present situation poses, however,
an important question to today's restorers.

The Restoration of Hagia Sophia
is extremely complicated and delicate.

The building embodies the history of Christianity
as well as that of the Eastern Roman Empire,…

…but it is also a very important mosque
for Islam and the Muslim world.

So the restorers are always
facing the inevitable question: …

"How do we restore Hagia Sophia?"

Which of its historical layers
should emerge?

This question is all the more sensitive,
because under the plaster layer from Ottoman times…

…there are even more mosaics.

Underneath, possibly,
also figurative ones,…

…because some drawings by Fossati
do not correspond to any of the mosaics visible today.

If that's the case, we still don't know
where exactly they are located.

On the other hand, it is unthinkable…

…to destroy all Ottoman decorations,
just to find these mosaics.

It is possible that Hitoshi Takanezawa,
from Kobe University, will find a way out of this dilemma.

We are currently developing
a new research tool,…

…a technology that can be used to determine
whether there is a mosaic underneath,…

…without destroying anything.

Hitoshi Takanezawa wants to scan the walls
of Hagia Sophia with an electromagnetic detector.

This device is usually used for tracking
hidden defects in buildings
such as bridges and skyscrapers,…

…and leaves the wall surface intact.

But Hitoshi Takanezawa has yet to prove
that this procedure is actually suitable here.

That's why he concentrates first
on small areas already free of plaster,…

…on which colored mosaic stones
have already come to light.

We're sure that under that plaster, which has
a geometric or plant pattern, a mosaic is hidden.

If the mosaic continues under the plaster,
and the scanning procedure works,…

…the image should be recognizable.

The scanner emits electromagnetic signals
into the different wall layers.

When the waves hit a metal surface,
they are reflected.

So the echo allows the reconstruction
of the metal elements present in the wall.

Hitoshi Takanezawa hopes
that this procedure will profit…

…from the preference of the Byzantine artists
for silver and gold tesseræ.

This trace is from metal tesseræ.

Therefore, we believe – or hope –
to find geometric patterns with our instrument.

We scanned the site 5 times,
and this green zone here is from metal tesseræ.

And here is a circle.

It's definitely made by human hands.

Encouraged by this result, Hitoshi Takanezawa
goes to the top floor of Hagia Sophia.

A narrow gallery runs along the tympanum,
at the level of the base of the arch.

The entire upper part of the structure
was once covered with mosaics.

The question now is,…

"At what point should he begin
the search for figurative motifs?"

It's very hard to decide
where to start looking.

The area is huge,
so I have to rely on my intuition.

Originally, this niche contained
images of saints or archbishops.

Like over there!

On the opposite North side,
the niches are decorated with human figures.

Fossati's drawings indicate
that this page had similar motives.

But have those works
also survived the centuries?

Some wave reflections
have been detected here.

This would indicate that there is metal
under the plaster layer.

We assume that these
are the remains of mosaics.

With 70% certainty!

Hitoshi Takanezawa is not the only one
examining Hagia Sophia's walls.

The restoration team
is doing the same.

Although the plasticity of the mortar
gives Hagia Sophia anti–seismic properties,…

…but they also have a downside.

The suppleness of the mortar of Hagia Sophia
is caused by high humidity.

But this moisture is also damaging to the mosaics,
the plaster, and the stone facings in the building.

We are now trying
the deformities…####

…– those caused by the moisture
formed on the various surfaces –…

…to eliminate.

Before the restorers intervene,…

…they document exactly
– as was done before by Whittemore and Fossati –,…

…every centimeter of the building.

In contrast to then, however, technologies
such as laser scanning are available today.

Besides, the engineers are investigating
whether the walls have water infiltrations…

…or show any other
hidden signs of deterioration.

Although it's not their main goal,
they might, like Fossati,…

…come across, by chance;
upon figurative mosaics as yet unknown.

We haven't yet discovered any mosaics
under the plaster.

Maybe that will happen
during the second phase of our work.

I know that the records of Fossati's restoration
give evidence of such finds,…

…but we haven't yet
discovered something like that.

The walls of Hagia Sophia
seem to keep their secrets very well hidden.

So far, Hitoshi Takanezawa
couldn't find any hidden treasures.

Detailed analyses have shown…

…that the echoes detected on the ledge
were not due to mosaics.

We did a scan there,
and recorded several reactions,…

…but they seem not to come from mosaics,
but from metal parts that reinforce the construction.

The recording actually shows
just several horizontal lines,…

…and that's why we came to the conclusion
that this is not a mosaic.

At the other place where he tested his method,
it could be determined with certainty…

…that the mosaic
continued under the plaster layer.

But, because of the lack of precision of the apparatus,
the subject could not be identified.

That's why Hitoshi Takanezawa
makes researches in the Fossati archive.

Perhaps, among the unpublished drawings,
he will find one…

...that assists him
in the interpretation of his results.

Despite disappointed hope,
he doesn't give up.

There is a sketch by Fossati
of a circular mosaic.

But experts don't agree
on where it might be.

The drawing refers to the pictorial scheme
of the "Majestas Domini", or "Ruler of the World".

This type of image can be found
very much on the center of a Byzantine dome.

Hitoshi Takanezawa thinks he knows
where to look for it.

A hypothesis says that at the top,
in the mighty dome of Hagia Sophia,…

…the face of Jesus
could be pictured over a large area.

The dome is at present covered
with stucco and verses from the Koran,…

…but if we could discover that icon
with an electro-magnetic scan,

…that'd be wonderful!
That is my dream!

But what should be done
if that dream comes true?

If there are still
many unknown mosaics in Hagia Sophia,...

…then they should definitely
be brought to light.

The only valid exception I would make would be
if they were located beneath a later decoration.

For example, it is very likely
that the dome was indeed decorated with mosaics.

But the dome is now decorated
with precious calligraphy.

Maybe this serves as a comparison: …

…if there was is a Byzantine icon and – let's assume –
Rembrandt had painted something over it.

It does happen that painters sometimes
reuse an old canvas or an old wooden panel.

Would you remove the Rembrandt
to uncover the icon?

Probably not.

But this question is moot…

…if the building is not made safe against the great earthquake
that threatens to affect Istanbul at some point in the future.

Everything is finally ready
for the test in the seismic laboratory.

The vibrating table
is set for an earth quake of 7.4 magnitude.

A similarly powerful earthquake
destroyed parts of the city in 1999.

The duration of the shock
is limited to 3 seconds,…

…which is proportional to the model size
in relation to the real size.

The model has withstood the first test so well
that the engineers want to subject it to a stronger shock.

We amplify the tremor amplitude:
it is now 2.2 g.

You said 2 is the max.
Now we're above it.

If possible,
let's go up to 2.4 g.

Extrapolated to Hagia Sophia,
the next test shock corresponds to an earthquake,…

…stronger than any
previously recorded in Istanbul.

There is a new crack
in this arch!

But it is amazing that the half–domes,
contrary to our fears, show no new damage.

Since the essential components have remained undamaged
in the test, there can be hope for Hagia Sophia.

But, in order to find out
the locations of the structure vulnerabilities,…

…the experiment will be pushed
to its extreme limit.

We have already exceeded
the nominal capacity of the vibrating table,…

…but it can take
a little more.

The thrusts, at maximum force,
will now be even be repeated several times.

The question is no longer,
"What earthquake magnitude
will Hagia Sophia be able to endure?",…

…but where
the weak points are located.

The model may be about to collapse,
BUT it still holds up.

There are two particularly vulnerable parts: …

…the half–domes and the arches.

It's only a matter of time,
which one falls first.

Everyone is eagerly awaiting the collapse
of the half–domes and arches,…

…but no one has any idea
what exactly will happen.

In slow motion mode, you can see how the half–domes
have detached themselves from the rest of the structure.

After losing their supports,…

…the arches have widened,…

…and that has collapsed the dome.

It would be premature
to draw any final conclusions,…

…but the experiment shows…

…that the continued existence of Hagia Sophia
is by no means due to a miracle.

If there is a miracle, then it is based
on the architectural design itself.

All elements
that make up the main structure…

…work harmoniously together.

The builders wanted Hagia Sophia
to endure forever.

Therefore, they used the greatest talents,
the most skilled craftsmen, and the finest materials.

The careful design of the building
also took the earthquakes into account.

All of these factors
work together,…

…and then this building came into being,
which has endured for so many years,…

…and which exist
for many years to come.

Chances are that this profile,
designed in the 6th century
to give a message to the world,…

…will still tower, for a very long time,
over the old town of Istanbul.

But today Hagia Sophia is threatened
by an earthquake of a completely different kind.

Because the current
Turkish government wishes…

…to break
with the secular ideal of Atatürk's,…

…and to give religion again a more important place.
in the government of the country,…

…part of the population
is resisting against such change.

The future of Hagia Sophia
depends on the issue of this conflict.

Its symbolic value is unbroken,…

…and official announcements are piling up,
affirming that the reconversion of the museum…

…into a mosque,
is a necessary step.

It may be that the AyaSofya, in many ways,
reflects the current tensions.

I believe that people
who want to use it again as a mosque,…

…are at one end of the political spectrum,…

…and those who, like myself,
wish that it remain a museum,…

…are at the other end of that spectrum.

I think we could use Hagia Sophia today
as a symbol of Turkey's rich multicultural history.

It doesn't belong
to any particular ethnic or religious group.

It is a monument that symbolizes
the entire eventful history of this country.

Hagia Sophia
still stands today…

…thanks to the fact,…

…that all the civilizations that followed one another
at the frontier between Europe and Asia…

…respected this building,
and equally took care of its maintenance.

That applies also to the historians and engineers
who deal today with the conservation of this unique building,…

…beyond the current political conflicts.

Hagia Sophia
has its own identity.

The role that people impose on it
is not relevant to us.

Our only aim is to preserve it
for future generations.

As an architect, I think
it is a monumental and unique creation.

We want it preserved, in its present condition,
inside and outside, for future generations.