Original subtitles

(male narrator) Ancient sites

with hidden powers

to turn light from outer space

into spectacular special effects.

Did Roman emperors harness the power of the universe

to awe and terrify the people of Rome?

We uncover the last, great mysteries

of the ancient world's greatest empire.

Ancient mysteries,

shrouded in the shadows of time.

Now, can they finally be solved

by looking to the heavens?

The truth is up there,

hidden among the stars,

in a place we call...

The Universe.

The ancient monuments of Rome.

Millions of tourists photograph them every year.

But is there more to them than people guess?

There's new evidence

that these ruins were once machines,

designed by Rome's emperors

to connect their power with the sun.

The evidence may be here,

in a temple in the heart of Rome

that has survived nearly intact

for almost 2,000 years.

The Pantheon.

World famous for its concrete dome

and the 27-foot hole in its center

called the "oculus," or eye.

Sunlight flows in from almost 15 stories

above the Pantheon's marble floor,

providing the main room's

only source of natural light.

But is there also something far more mysterious going on?

Professor Robert Hannah thinks there is.

Now, I'd been going into the Pantheon

how many times over 20 or 30 years

and not even thought of this.

But some years ago, I was working

on aspects of Roman time,

and I came across the idea that, in the Pantheon,

what we seem to have is a monument

that is able to capture the sun

by subtle means in the decoration

and in the architecture.

(narrator) As evidence for his startling theory,

Hannah points to the way the oculus focuses sunlight

on different parts of the Pantheon

at different times

on the longest and shortest days of the year,

the summer and winter solstices.

And especially on two days

that to the ancients symbolized a great cosmic balance.

The Equinoxes.

Roughly speaking, the Equinox is a time

when day and night balance each other.

12 hours of day, 12 hours of night.

(Johnson) The tilt of the Earth's axis

means that different parts of our globe

are closer to or further away from the sun

as we go around the sun.

We have two equinoxes because we have

two positions when the tilt of the Earth

is neither toward or away from the sun,

twice a year, six months apart.

So roughly in the third week of March

and the third week of September,

we have equal day and equal night.

(narrator) Are these solar movements marked

inside the Pantheon?

The equinoxes are halfway through the cycle

of the sun in the course of the year.

At noon, halfway through the day,

the sunbeam strikes the point halfway up

the interior of the building,

where the cylindrical wall

meets the base of the dome.

That has to be more than coincidence.

All of it is midway points in time and space.

(narrator) But was this really a part of the original design?

Just because you see an astronomical alignment today

doesn't mean it existed 2,000 years ago.

It's possible that when the Pantheon was built

around the year 125,

the ancient sky would've lined up

differently with the building.

Hannah's ideas are put to the test

at Indiana's Ball State University.

The members of the virtual reality team at IDIA Lab

are experts in examining astrological alignments

at ancient sites,

including Stonehenge.

Based on the latest research

and archeological findings,

IDIA Lab recreates with pixels

what the Romans built with concrete and bronze.

The Lab's computers can then simulate

the exact location of the sun

for any date in time

over a period of 20,000 years.

Neil, let's go ahead and just kind of

take a 360 degree pan.

Look at the dome, also the central oculus.

Let's go over to the celestial simulation interface.

(narrator) Hannah's theory could stand or fall

because of one cosmic fact.

Over time, the dates of the equinoxes change.

(Filippenko) The day is not exactly 24 hours long.

An exact 24 hour day would be

86,400 seconds long.

But right now, in fact,

the day is 86,400.002 seconds long.

Now, over the centuries, that actually adds up.

(Fillwalk) The dates of the equinox do change over time.

If we're talking about back to the Roman era,

you may find that they're several days off.

(narrator) Does that sink Hannah's theory?

Let's go ahead and look at the equinox.

(narrator) IDIA Labs spins back the clock

to the era when the Pantheon was built

and dials in the date of the equinox.

The effect is clear and stunning.

At the equinox moments, vernal and autumnal equinox,

we see the sun disc being perforated by

the Coronus element.

(narrator) It turns out that the sheer size of the Pantheon,

with its massive circle of light,

counteracts any slippage in the timing of the equinoxes.

It was an intentional effect

and it was designed to last for millennia.

But if the Pantheon was designed to track solar events

like equinoxes, then how, using only technology

available to the ancients,

do you design a building that will focus the sun

where you want it at certain times of the year?

First, you take a year to plot out

the sun's apparent path

to cross the sky.

From rising and setting

to solstices and equinoxes.

Once you know where the sun will be,

you can set up a device to mark its movements.

The sundial,

one of the first ways the ancients brought

the power of the universe down to Earth.

The sundial tells time with a blade

that blocks the light and casts a shadow.

(Kaku) Take a look at the shadow of a sundial.

As the sun moves, it traces out

a motion of the shadow.

You divide it into 12 pieces,

and that becomes the hours of the day.

(narrator) But does that mean that

the Pantheon is a 2,000 year-old sundial?

Some scholars challenge the idea,

saying that the Pantheon isn't built like an ordinary sundial

with a blade.

A historian had written up an article, said,

"It doesn't work."

And I thought, "You're using the wrong type of sundial."

(narrator) The answer may lie in a different kind of Roman sundial,

a hemicyclium,

essentially a stone bowl

with a hole angled towards the sun.

This is a mock-up of a hemicyclium.

In ancient Roman times, it would've been made of stone.

Here is the noon timeline

and the hours of the day.

And if you can see it,

a beam of sunlight is projected on the interior.

With this kind of sundial, you're marking time

not with a shadow, but with sunlight.

(narrator) So, the Pantheon is like an inverted hemicyclium.

You're inside a sundial, where time is told by light.

As the sun moves around, the light from the oculus

also moves around the building.

It's an incredible feat of architecture.

(narrator) But did the Pantheon have a higher purpose

than simply marking time?

Is a deeper meaning revealed

on a certain day in spring?

A colleague of mine, Julie O'Malley,

discovered that on the 21st of April

at noon,

if you stand in the doorway of the Pantheon,

you are bathed in that beam of light.

(narrator) But why April 21st?

It's nowhere near the equinoxes or other major solar events.

And why light up the doors?

Unless someone is coming through.

21st of April, so what?

Well, that's a very ancient festival.

It is the traditional founding day of the city of Rome.

So, April the 21st is a big deal.

(narrator) How does all of this connect with the sun

lighting up the doors of the Pantheon?

The team at IDIA Lab has the answer.

It all goes back to the man who oversaw

the Pantheon's construction,

the emperor Hadrian.

IDIA Lab confirms a precise midday alignment

during Hadrian's reign.

So, on April 21st, the sun lights up

the entrance to the Pantheon

perfectly, like a theater spotlight.

And so, if somebody were to come in,

let's say the emperor, Emperor Hadrian,

they'd walk in and they'd be illuminated

by the light on that day,

and that date happens to be the birthday of Rome.

Marking the entrance of the emperor,

coming in style, announcing,

"Here I am!"

(narrator) If Hadrian did turn the sun into his personal spotlight,

it would be the ultimate ancient special effect.

But it wasn't just for show.

By creating a machine to capture and control the sun,

Hadrian was demonstrating his power,

not just over Rome,

but over the heavens.

How can we be sure Hadrian built the Pantheon

so he could command the sun?

Because emperors before him also built monuments

to capture the sun for their own glory.

Including one that caught the sun

on the anniversary of Rome's most infamous murder.

(narrator) To scientists, the sun is our nearest star.

A ball of hydrogen and helium,

330,000 times the mass of the Earth,

with a core temperature of 27 million degrees.

But to the ancient Romans,

the sun was a god.

(Kaku) First of all, it's the giver of life.

Without the warmth of the sun,

we're plunged in darkness and we freeze to death.

Second of all, it is the dominant object

in the heavens.

(narrator) Romans worshipped the Greek gods

Apollo and Helios,

both of whom were often shown driving the sun.

From our vantage point here on Earth, it appears

that the sun travels across the sky in its path,

leading to the ancient belief

that it was carried by gods and their chariots.

(narrator) The Romans also had their own sun god,

Sol.

So it makes sense that the emperor Hadrian

would've constructed his Pantheon

to align with the sun.

But how do we know these alignments

were intentional?

One form of proof would be to find evidence

that Hadrian was building on a tradition

established by earlier emperors.

Could that evidence be found

just over a mile north of the Pantheon?

This is the Ara Pacis,

or "Altar of Peace."

Built by Rome's first emperor,

Augustus Caesar, in 10 B.C.

The Altar of Peace represented the end

of a century of civil war.

So, building an altar of peace

is a major propaganda exercise.

(narrator) Directly opposite the altar,

Augustus set up a 600-year old,

71-foot tall,

red granite obelisk,

transported from the conquered nation of Egypt

and dedicated to the sun god.

But why use an Egyptian monument in Rome?

The Romans knew that in ancient Egypt,

the obelisk was a symbol of a ray of the sun.

(narrator) The Egyptians used obelisks as billboards

to advertise the achievements of various pharaohs.

But Augustus repurposed this centuries-old obelisk

as something new,

the giant blade of a sundial.

I think that we definitely should think of

these ancient tools as technology.

They may not be electronic, per se,

but they were certainly tools to learn about the heavens.

(narrator) Augustus created a giant calendar

that marked the days and the seasons.

But did Augustus go beyond this,

making this obelisk interact with the sun

in even more dramatic ways?

It's a challenging question to answer.

Unlike the Pantheon, this site has not remained intact.

The Altar of Peace has been relocated to a museum.

The obelisk was toppled in an earthquake,

restored in the 18th century,

and moved.

It stands today several blocks from its original location.

So the ancient alignment has been destroyed,

and it's up to the virtual reality team

at Ball State University's IDIA Lab

to make the past live again.

With onsite data surveys,

GPS information,

and NASA observations,

they recreate the original positions

to see what special effects

the altar and obelisk may have created

with the sun.

In doing so, IDIA Lab discovers something astonishing.

On one special day,

the obelisk's shadow would've climbed the marble stairs,

moved through the altar itself

and continued out the other end,

penetrating the building.

It pierced the heart of the altar like a knife

on March 15th, the Ides of March.

The date in 44 B.C. when knives pierced

the heart of Augustus's predecessor,

Julius Caesar.

Even more amazing,

the shadow of the obelisk

cut through a rectangle of light

created by the opening of the altar.

Did the light represent Caesar's body?

Or possibly another object from the heavens?

In 44 B.C.,

a few months after Caesar's assassination,

a comet appears in the skies over Rome.

Augustus, Julius Caesar's adopted heir,

promotes the idea that the comet is Caesar's soul

transformed into a god.

Augustus very cleverly made Julius Caesar a god,

and therefore himself son of a god.

No one had ever been that before.

(narrator) So perhaps the light bisected by the shadow

was intended to represent Caesar's comet.

But did Augustus symbolize his own godly power

with something more enduring?

Not a comet that fades away,

but the eternal sun.

The sun is dependable, it's reliable, it's glorious.

And you just look outside and there it is.

(narrator) With the altar and obelisk,

Augustus used the sun and stones to tell a story

of his own power.

He reminded Romans of Julius Caesar's godhood

and his own.

And by raising an obelisk to track the sun,

Augustus told the world that the heavens

were under imperial control.

So when Hadrian built his Pantheon

almost 150 years later,

he built on a Roman tradition

of aligning monuments with the sun

to create dramatic special effects.

Instead of an outdoor monument that used a shadow,

Hadrian built a dome

that turned the sun itself into a spotlight

for the emperor.

But was Hadrian also inspired by another emperor,

who many historians called mad?

New evidence may have solved this ancient mystery.

(narrator) To the ancients,

the wider universe was largely unknowable.

But they understood the importance of the sun,

and Roman emperors aligned their structures

to convey their control over our nearest star.

The emperor Hadrian may have designed the Pantheon

so he could make a propaganda appearance

bathed in sunlight on Rome's birthday.

But was Hadrian inspired by

the most notorious emperor of them all,

Nero?

(Markley) Nero was the man in charge

while Rome's burning.

He was the one who burned Christian martyrs.

So he goes down in history as a bit of a monster.

(narrator) But did this man, whom history calls a monster,

consider himself a god?

By the time you get to Nero,

you start to question whether

the living emperor is a god.

In particularly the sun god, Sol.

Nero adopts the radiate crown of the sun.

We see it in his coins.

(narrator) Some say Nero even turned himself into the sun god

in the form of a Colossus

over 100 feet tall.

But Nero's earthly glory didn't last.

He was deposed

and driven to suicide.

With the hated emperor dead,

the Romans had to decide what to do about his Colossus.

There is an attempt to remove

the association with Nero

and simply say it is a statue of the sun god.

The statue is physically moved from its spot

slightly over to an amphitheatre.

(narrator) The Colossus gave the amphitheatre the nickname

it's kept for 2,000 years,

the Colosseum.

As for the Colossus itself...

The Colossus is lost.

We have rediscovered parts of its base,

but the statue itself has disappeared.

(narrator) Most of ancient Rome's sun-related structures

have vanished or lie in ruins,

with connections that can only be recreated in virtual reality.

But parts of Rome's obsession with tracking the sun

are very much alive.

Today, many people feel like slaves to their schedules.

Everything from clocks to phones tells us we're running late.

Over 2,000 years ago,

the ancients got stressed in the same way

about sundials.

It seemed like the government

was setting these devices up everywhere

to regulate the heavens and people's lives.

When sundials first came in, they are a newfangled machine.

And the people are complaining about

the tyranny of the sundial.

The way the joke goes is that,

in the past you used to know when you could have

your dinner or lunch because your stomach told you.

Now we have to wait until the sundial tells us.

(narrator) While ordinary people had to obey the sundial,

the emperors used sundial technology

to celebrate their own power.

One amazing example survives

in the ruins of one of Nero's palaces.

The Octagonal Room,

an eight-sided chamber open to the sky.

The dome and oculus probably inspired the Pantheon's dome

two generations later.

When you walk into Nero's octagonal room,

it really is quite striking that you get this

distinction between strong light and strong dark.

And you're drawn immediately to the idea of

"that sunlight matters."

(narrator) Recent calculations reveal

that Nero's octagonal room and oculus

were perfectly designed to throw sunlight

on the main doorway, on the anniversaries

of key moments in the emperor's career.

The 5th of March was when Nero became Pontifex Maximus,

the chief priest, the person in charge

of the calendar and of time.

And the 13th of October,

the date of his accession as emperor.

(narrator) To celebrate his becoming the most powerful man in Rome,

Nero captured the rays of the most powerful star in the sky.

It's easy enough to imagine him

standing within the doorway, bathed in sunlight,

suitably dressed and attired

and capturing the sun in that way.

(narrator) If Nero made the sun seem to obey him,

this is tantalizing evidence

that he inspired Hadrian

to create an even greater solar spectacle

with the much larger Pantheon.

But Hadrian didn't stop there.

He created more solar special effects.

Not just in the Pantheon,

but in his own private city,

where today, at the summer solstice,

the setting sun lights up an empty alcove

in a ruined temple.

What sacred object once stood here?

It's a mystery that we may have finally solved.

(narrator) Rome's emperors took the ancient worship of the sun

and did something new.

Using building and monuments

to create the illusion that they controlled the sun.

In the Pantheon, Hadrian may have used

astronomy and architecture

to turn the sun into his personal spotlight,

reinforcing public perception

of his imperial power.

But new evidence suggests

Hadrian built other solar-connected structures,

for more mysterious, private purposes.

He built them here, on 300 acres outside Rome.

It's called Hadrian's Villa,

but it was much more than that.

(Markley) We're here at the Getty Villa in Malibu,

and it's based on the private residence

of a very wealthy Roman.

Hadrian's Villa, that's 20 times bigger!

That's the kind of residence

that only an emperor could afford.

It was Hadrian's Rome away from Rome.

(narrator) Hadrian had complete control over his villa's architecture.

And as our virtual reality investigators

at Ball State University's IDIA Lab reveal,

he created dramatic solar effects

in places throughout the complex.

This is the axis that the sun

would travel and send light down

on summer solstice sunset.

(narrator) One temple, called the Roccabruna,

lines up with a structure called the Accademia,

or "Academy," and both buildings line up

with the summer solstice.

(Fillwalk) On that summer solstice event,

the sunset rays of light

would penetrate the upper temple door of Roccabruna,

all along the pathway

and go down into the Accademia site itself.

During the spring, the sun appears progressively

higher in the sky each consecutive day.

Until it's at its highest point.

That's when the Earth is tilted toward the sun

the most that it ever is.

That's the summer solstice.

The Earth is not vertical with regards

to the plane of the solar system.

It's tilted roughly 23 degrees.

As the axis tilts away from the sun,

the northern hemisphere gets less sunlight.

It is the shortest day of the year.

It is the winter solstice.

On the left hand, we see that the axis points toward the sun.

The northern hemisphere gets more sunlight,

and this is roughly the summer solstice,

the longest day of the year.

(narrator) But the Roccabruna does more

than just line up with the solstices.

In the 1980s,

architects Robert Mangurian and Mary-Ann Ray

discovered an even more mysterious effect inside.

On the summer solstice,

the light of the setting sun

fills an empty alcove

while a conduit

focuses a blade of sunlight

just above the space.

IDIA Lab's calculations show

that the effect was even more impressive in Hadrian's time.

The summer solstice light comes through and creates

a very precise, almost sort-of gunsight

kind of event on the back of the temple ceiling.

There's absolute precision about that,

which is really exciting, I think.

It's not one of these general alignments.

It's a very, very precise alignment.

(narrator) The blade of light seems to point down

at the illuminated alcove,

which wasn't always empty.

The Roccabruna is built in such a way that on the day

of the summer solstice,

the sun shines directly through the window,

down to a spot where a statue stood.

Now, the problem here is, we don't know what the statue was.

(narrator) What figure was so important to Hadrian

that he wanted it illuminated on that one special day?

There are various theories.

It could've been a statue of the emperor Hadrian himself.

(narrator) It would help if we knew why the Roccabruna was built.

Based on archaeological evidence,

the digital detectives at IDIA Lab

reconstruct the original, three-level structure

that, like the much larger Pantheon, was designed

around an imaginary sphere.

But the purpose remains mysterious.

And whatever statues once stood inside

were stolen centuries ago.

Many are scattered in museums around Rome.

But if we can find the right statue for the alcove,

the purpose of the Roccabruna

and its dramatic solar spotlight

might be revealed.

Archaeologist Marina De Franceschini

and archaeoastronomer Giuseppe Veneziano

uncover a telling clue.

A marble candelabra in the Roccabruna

bore Egyptian images,

including snakes and a musical instrument

associated with the Egyptian goddess Isis,

a goddess also worshipped by many Romans,

including, perhaps, Hadrian.

The Isis cult centered around a lot of healing,

and there's also an aspect of reincarnation,

return from the dead...

(narrator) And an important day of celebration in the Isis cult

was the summer solstice.

These clues lead archaeologists

to comb through the catalogue of treasures

looted from the villa.

They find no fewer than four statues of Isis

in various museums.

The statues of Isis were situated within the villa site.

In thinking about Roccabruna,

the summer solstice is also a feast day for Isis.

So it seemed to be a logical connection.

(narrator) But would an Isis statue fit into the space

of the empty alcove?

IDIA Lab calculations show it would.

We've proven that there actually is a substantial

solar alignment that's significant on that date.

So, when we did the reconstruction

working with the scholars,

the advised us to place the Isis in that main central niche.

(narrator) So, we have evidence that a statue of Isis

stood here, but why?

Perhaps, Hadrian built this temple as a kind of machine,

to focus the sun's rays

and honor the great goddess who promised eternal life.

But Hadrian also controlled the sun

in another part of his villa

that's been hidden for almost 2,000 years.

A mysterious temple with a surprising connection

to Egypt.

The temple was dedicated to Hadrian's one great love...

and it wasn't his wife.

(narrator) Hadrian's Villa,

17 miles east of Rome.

Here, almost 2,000 years ago,

the emperor Hadrian created solar special effects

for his own private purposes,

including in one place that was forgotten for centuries.

A mysterious temple not unearthed by archaeologists

until 1998.

Up until recently, they didn't know

it really even existed because...

Earth had replaced what little was left.

(narrator) Based on detailed archaeological evidence,

the temple rises again in virtual reality.

But as the team at Ball State University's IDIA Lab

fits the puzzle pieces back together,

new mysteries arise.

Why would a Roman emperor build an Egyptian temple

with an obelisk

and statues dedicated to the Egyptian god of the dead,

Osiris?

According to myth,

Osiris drowned in Egypt's Nile River

before being brought back to life by his wife,

the goddess, Isis.

(Markley) Osiris was resurrected.

Therefore, Osiris becomes associated with immortality

or what happens after you die.

(narrator) But there's something odd about the statues of Osiris.

While they have the costume of the Egyptian god,

they have the body and face of a real man.

And not just any man.

It's Hadrian's lover, Antinous.

Hadrian met Antinous when the emperor was nearing 50

and Antinous was 12 or 13.

The two became inseparable,

but when Antinous was about 19,

during an official tour of Egypt,

he fell from Hadrian's barge into the Nile and drowned.

(Markley) Was it an accident? Was it a murder?

Was it jealous political rivals?

Was it even a human sacrifice

to try to restore health to the emperor, Hadrian?

That was one of the rumors.

So we really don't know exactly how and why Antinous died.

What we do know is, Hadrian was heartbroken.

(narrator) Hadrian set up statues, shrines, and even cities

dedicated to his lost love all over the empire.

And that was just the beginning.

Hadrian announced that Antinous was to be deified.

This really didn't accord with Roman tradition,

but he was the emperor and he wanted Antinous deified,

so deified he was.

(narrator) And because Antinous died in the Nile,

Hadrian reimagined his lover as Osiris,

the god who died in the Nile and was then reborn.

But the temple of Antinous hides one final surprise.

Because when the virtual reality investigators

restore the obelisk, rebuild the shrine,

and set up one of the statues of Antinous as Osiris,

they find something totally unexpected.

Neil Zehr, one of our staff members,

noticed that on a certain date

the shadow of the obelisk that was in the temple of Antinous

crossed the statue of Antinous, and he thought,

"Hmm, isn't that interesting?"

(narrator) The date of the alignment was the 20th of July,

an ancient symbol of rebirth,

because July 20th was New Year's Day.

But not in Rome.

In Egypt.

The Egyptian New Year began with

the flooding of the Nile,

signaled by the reappearance after months in the underworld

of the star of Isis.

(narrator) Because of the way the Earth turns,

different stars are seen at different times of the year.

July 20th marked the pre-dawn return

of a star sacred to Isis.

The brightest star in the sky.

Known to the Romans, and us,

as Sirius.

To our eyes, Sirius appears in the night sky

to be a single star.

But in fact, Sirius is actually a binary star,

or two stars that are associated with one another.

(narrator) 8.6 light years from Earth,

Sirius is twice as massive as our own sun

and 20 times as powerful.

Its companion, Sirius B, is a white dwarf.

But to the Egyptians,

the binary star was a single light

whose return on July 20th

meant that the Nile would once more give life to the land.

And so, Hadrian honored his lover with an obelisk.

Like the blade of a giant sundial,

this caught the sun and cast its shadow

on Antinous as Osiris

on the day the star of Osiris's wife

brought new life from the Nile.

A complex symbol of rebirth and resurrection.

At his villa, Hadrian used his mastery

of architecture and astronomy

to create special effects with the sun

and honor his lover's memory.

But could the emperor maintain his solar power

after his own death?

As it turns out,

Hadrian may have had a plan

for his own immortality.

(narrator) Ancient buildings in and around Rome

that have intricate connections with the sun.

Is this one of them?

The Castel Sant' Angelo,

about a mile northwest of the Pantheon.

Today a museum,

but in the year 138,

the mausoleum of the emperor Hadrian.

A tomb that may have contained

Hadrian's final solar special effect.

The tomb of Hadrian probably had a statue of him

in a chariot pulled by four horses.

Like Apollo, who would have a chariot

pulling the sun through the sky.

(narrator) The statue alone would identify Hadrian with the sun forever.

But did the emperor go even further?

In life, Hadrian built the Pantheon

as a giant sundial

and turned the sun into an imperial spotlight.

He set up temples to make the sun honor the goddess Isis

and his dead lover.

Preparing for his own death

and his elevation to full godhood,

Hadrian also designed his tomb

as a final trap for the sun.

Recent calculations reveal an astonishing alignment

at the summer solstice.

IDIA Lab confirms that looking from the steps of the Pantheon,

Hadrian's sun god statue would have been

dramatically silhouetted by the rays of the setting sun.

Another link there to Hadrian and the sun.

(Fillwalk) The Pantheon is oriented so it faces the mausoleum.

When it was constructed, that whole field was empty,

so you could see from the steps of the Pantheon.

You could see the mausoleum.

Today in Rome, both those structures exist,

but you can't see them because

there are city buildings in between the two.

(narrator) Using the sciences of astronomy and archaeology,

and the power of virtual reality,

the mystery of the Pantheon has finally been solved.

Its oculus is just one of many ways

that Hadrian captured the sun.

Building on a tradition that began

with Rome's first emperor, Augustus,

and continued with Nero and his octagonal room.

But if Hadrian's Pantheon

boasted Rome's greatest solar special effect,

the obsession of Rome's emperors with the sun

didn't end there.

80 years after Hadrian's death,

a new kind of sun worship comes to Rome,

from the stars.

Sometime in the past, it was said,

a meteorite fell in Syria.

It was obviously a sign from the gods

or a god itself.

The rock, shaped like a black cone,

was worshipped as the representative of the sun god.

Incredibly, in the year 218,

after a coup d'etat,

the power of the Roman state

was handed over to the chief priest of the sun cult,

a 14 year old named Elagabalus.

Elagabalus decided to import that entire sun cult

directly to Rome.

He brought the stone to Rome

and introduced the sun god

as the primary deity of the entire city of Rome.

(narrator) Rome's new number one god

was Sol Invictus,

the unconquered sun.

But Romans weren't ready to have all the gods of Olympus

take second place to a stone from Syria,

even if it had fallen from the sky.

Elagabalus was murdered

in another coup d'etat.

His sacred meteorite was shipped back to Syria.

Then, almost 60 years later,

Roman religion faced growing competition

from Christianity.

The emperor Aurelian brought back Sol Invictus.

Perhaps to counter the one god of the Christians.

And at that stage, the sun god Sol

becomes the chief god of the Roman Pantheon.

(narrator) But the sun god's reign was short.

In the fourth century, Rome became Christian,

and so did the emperors.

The old monuments fell into ruin

or were also converted to Christianity

like the Pantheon,

which is now a church.

But although the sun god is gone,

the sun still shines.

And this church still displays

the 2,000-year old

solar special effects of ancient Rome.

And atop Hadrian's tomb,

his sun god statue has been replaced

by the archangel Michael.

But the angel is still lit at the summer solstice

by the eternal rays of the setting sun.