Original subtitles

(dramatic music)

- [Narrator] Since the dawn of human history,

civilizations have gazed up to the stars

to make sense of our existence.

The cyclic patterns of celestial bodies

guiding our understanding of ourselves

and the world around us.

The intricate carvings

etched into the sandstone structure of Angkor Wat

tell us a story written in the skies.

Every inch of this ancient complex is coordinated

with the cosmic realms.

- Angkor Wat is basically a three dimensional reflection

of the Hindu universe in cosmology.

- [Narrator] In Mexico, the ancient Mayan building,

a ladder to the heavens.

The pyramid of Kukulcan is a wonder of the world

shimmering with solar alignments.

- It's actually a pyramid built on a pyramid,

built on a pyramid.

- [Narrator] What secrets contained within

potentially unlock a gateway to other dimensions?

A strange earthen mound in Ireland curiously captures

the inaugural rays of solstice sunlight.

- On the day of the winter solstice, the sun would penetrate

to the very back chamber of the passage tomb.

- [Narrator] What were the motives

of its mysterious architects

and how exactly did they forge this link

between earth and sky?

(dramatic music)

(bright music)

In the light of Cambodia's rising sun,

stands a temple unlike any other.

Its sandstone spires seemingly reaching the heavens above.

- Sprawling over 400 acres, Angkor Wat

is the largest religious monument ever built.

It's truly a wonder of the ancient world.

- One of the things that is so striking

is how massive the actual site is.

So there is like the Angkor Wat temple,

but then there's all the other temples

that are part of the whole cultural site.

- Angkor Wat without question

is one of the great marvels of human engineering,

but it's also a stunning work of art decorated

with innumerable bas-relief sculptures.

It is surrounded by an enormous moat

in a beautiful landscape.

It is one of the great contributions to human engineering.

- [Narrator] Built by the rulers of the Khmer Empire,

Angkor Wat is a relic of the 12th century, a mighty monument

to a civilization largely reclaimed by the jungle.

It stands as a keeper of ancient stories etched in stone

and serves as a cosmic blueprint

with divine symbolism intricately woven

into its very foundations.

- The purpose behind its construction was

to have it embody the cosmos.

(bright music)

- Angkor Wat is basically a three dimensional reflection

of the Hindu universe in cosmology.

- From its foundation to its peak,

every element of this temple symbolizes the higher realm.

- How were its ancient architects able

to achieve such detail and precision?

And why was Angkor Wat ultimately left

to be reclaimed by nature?

- [Narrator] In the mid 19th century

while traversing the dense landscapes of Southeast Asia

in search of natural specimens, French Explorer Henri Mouhot

stumbles upon a remarkable discovery,

a massive 3.6 kilometer stone wall guarding a series

of raised galleries

and a quintet of tall towers, the tallest

of which stretches 65 meters into the sky.

In his writings, Mouhot declares the temple a rival

to that of Solomon, erected by some ancient Michelangelo

and proclaims it grander than anything left to us

by Greece or Rome.

- He's simply awestruck by the complex.

It affects him so profoundly, he compares it

to the pyramids.

- Angkor Wat is quite magical in a sense

that it's very intertwined with the nature around it.

Over time, they have sort of become one and the same.

There's still parts of the complex today,

so not Angkor Wat proper,

but the surrounding complex

that give people the same vision

as the French Explorer coming across

the temple for the first time.

So it's almost like you're discovering parts

of this complex yourself when you're walking

to some of the more remote areas.

- [Narrator] Though this age old structure

had been known to local peoples

and other foreign visitors for centuries,

the nature of its true origins

and purpose long remained a source of speculation.

Legends spoke of divine architects

constructing the temple in a single night

or giants raising it from the earth.

However, we've since pieced together

a more comprehensive picture

tracing the building's foundation

to the mighty Khmer Empire of the 12th century CE.

- The Khmer Empire was one

of the most advanced civilizations of the ancient world.

They were incredibly sophisticated builders and craftsmen,

and they profoundly shaped the history of Southeast Asia.

They ruled for six centuries over a vast empire

stretching from southern China to southern Vietnam,

from Burma to the Mekong River.

- [Narrator] At its heart lies the capital of Angkor,

a metropolis unrivaled in its time.

Home to nearly a million citizens at its peak,

it was once the largest pre-industrial city on earth.

- Angkor Wat stands as one

of the few remaining architectural marvels of this people.

- One of the reasons why there's

so few architectural remains of the Khmer Empire

is because of the fact

that they dedicated stone constructions to deities

and gods versus common people,

which would live in wooden structures

and haven't survived the test of time.

- [Narrator] The Khmer left few written records,

but their story is carved in stone.

Through these detailed bas-reliefs

and inscriptions, historians and architects

have begun to piece together the rise

and fall of this formidable empire.

In the early 12th century, King Suryavarman II ascends

to the throne commanding what had grown

to become a powerful empire.

- His reign marked the end of decades

of civil war and unrest.

He's an incredibly capable ruler.

He not only expands the empire through a mixture of warfare

and diplomacy, but he also fosters art

and culture within its borders.

- [Narrator] By 1122 CE, at the King's order,

work begins on Angkor Wat, a stone compound destined

to become the spiritual epicenter of the empire.

Carved from a sandstone canvas.

- Sandstone has been used to build everything from tools

to shelters since prehistoric times.

It's an incredibly durable material,

making it naturally resistant to harsh weather.

- If we think about Cambodia

and its climate, it's very susceptible to drought,

but also torrential monsoon,

so you're going to need a material

that's able to withstand both extremes.

- What makes Angkor Wat Angkor Wat is we're able to move

five to to 10 million shaped sandstone blocks into place.

They're each about 1.5 tons, so they're big

but not too big to slide around using incline planes

and rolling on logs.

- [Narrator] The magnitude of the material used

had puzzled researchers as there are no quarries

within the immediate vicinity of the site.

- Where did the stone come from?

If not sourced locally,

how did the 12th century workforce transport

such heavy materials from distant areas?

(dramatic music)

- [Narrator] Angkor Wat is likely supplied

by quarries at the base of Mount Kulen,

located 40 kilometers northeast of the temple.

It's initially hypothesized

that these mammoth stones were transported

via a circuitous route along roads and rivers.

However, in recent decades, satellite images

and LIDAR technology have revealed a vast network

of ancient canals, some of which trace a direct path

from Kulen to the temple grounds.

- The discovery of these canals indicates

that they may have used them for the transport

of their building materials.

- [Narrator] Even with a canal,

enabling direct delivery from the quarry to the jobsite

construction remained a massive undertaking.

- Some estimates say that there was

around 300,000 people supported

by a thousand elephants

working on the construction of this project.

- [Narrator] The full structure

takes over three decades to complete,

and although that might seem like a long time

by today's standards, it's speculated

that it would've taken their European counterparts

of the same period centuries.

Among the myriad of architectural wonders

scattered across Asia, Angkor Wat stands out

in more ways than one,

starting with its unique orientation.

- Most Khmer temples face the east

because Hindu deities normally sit facing the rising sun,

which is seen as a symbol of renewal and growth.

But Angkor Wat is oriented to the west

and this has puzzled researchers for centuries.

- [Narrator] Though unconventional, the precise position

of the temple facilitates a stunning celestial event

that occurs twice a year.

During the spring and autumn equinoxes,

times when night and day reach equilibrium,

the temple's central tower aligns perfectly

with the rising sun.

- In any culture that is building spaces

that's based on celestial events, the solstice, the equinox,

what we're seeing is that they're looking upwards.

When they're looking upwards, that's where you're dreaming,

where you're creative.

When you're actually operating

or getting things done, you're looking downwards.

That's when you're working with your hands.

When you manipulate the world, you look down.

You look up, when you're imagining

how the world is being manipulated.

- [Narrator] The Khmer understanding of the cosmos seems

to be embedded in nearly every element of Angkor Wat

and this spiritual journey begins at its perimeter.

- The moats around Angkor Wat are really quite impressive.

They're about a kilometer long on each side

and about two football pitches in widths.

When we look back at ancient civilizations

and their success, it actually has a lot to do

with control of water.

The most successful societies developed canals

and water control systems not only to irrigate their fields,

but also so that any structures

that they built remain stable over long periods of time

and work essentially sinking into the mud

or sinking into the ground.

- [Narrator] Given the immense height of the temple

and the region's volatile climate,

this moat is a careful design choice.

Khmer engineers construct the aquatic perimeter

to counterbalance the outward pressure of the shifting soils

beneath the temple's foundation.

- The moat was a crucial engineering decision

to ensure the temple's structural resilience.

- [Narrator] Without this imposing waterway,

the 900 year old structure would likely have

collapsed long ago.

Yet Angkor Wat's moat transcends mere practicality.

It also carries a profound spiritual significance.

- The moat surrounding Angkor Wat

represents the cosmic ocean,

a mythical body of water that marks the edge

of the universe in Hindu cosmology.

- [Narrator] Once across the threshold

into this symbolic realm,

visitors are greeted by an immense enclosure wall,

towering 4.5 meters and stretching over three kilometers.

Once through the gate, visitors enter the outer enclosure,

an area that is vast and open,

designed to make you feel small and humble in the face

of something far greater than yourself.

As you continue along the central path,

the journey becomes progressively

more focused on the divine.

The main tower of Angkor Wat rises at the heart

of the temple complex symbolizing Mount Meru.

- In Hindu cosmology,

Mount Meru is considered the mythical mountain

where the gods reside.

It serves as the central axes of both the spiritual

and physical universes.

- [Narrator] The temple comprises three ascending terraces

of galleries each rising higher than the last,

mimicking the arduous trek towards the heavens.

- The labyrinth of galleries guides visitors

into the center of a sacred shrine.

- [Narrator] Here, the walls come alive

with vibrant tales from Hindu mythology,

offering a first glimpse into the kings

and deities that inspired this grand design.

- Everywhere you look is an absolute masterpiece

of ancient Khmer sculpting.

(bright music)

- We know that there's hundreds

and thousands of different craftsmen

working to carve these reliefs,

but at the end of the day, it almost looks like it was done

by one master, just the uniformity of it.

- The bas-reliefs are extraordinary.

They are vivid.

They come out of the walls,

and one can imagine that as one enters the temple

during the height of the power of the Khmer people,

the bas-relief moving in the shimmering light

from the candles, it would've been very, very powerful

and mysterious.

Perhaps the most intriguing

and significant of the bas-relief is the enormous relief

that depicts the churning of the ocean of milk.

Now this is one of the most important stories

in Hindu religion and it speaks to the forces of good

and evil collaborating in pursuit of the elixir of eternity,

and it's dedicated to the god Vishnu,

the god who provided order

and the restoring of balance in society.

- King Suryavaman II fostered a devotion

to the Hindu god Vishnu.

This was a departure from popular Hindu sects at the time

who predominantly worshiped Shiva as their primary deity.

- Angkor Wat was dedicated to Vishnu.

Now there are reasons for it

that makes sense given the king.

First of all, he was the god of order and protection.

Secondly, the anchoring.

The westward facing orientation is intended to convey

that idea of order

because at two times of a year during the equinox,

it fills up with light.

Now, why is the equinox perhaps spiritually significant?

Well, the moment of equinox

is when night and day are equally long.

It's a time of balance and cosmic order.

- [Narrator] During the equinoxes, the shadow cast

by a pillar marks the opposing end points

of this bas-relief.

During the summer and winter solstices,

the longest and shortest days of the year,

the same shadow highlights the center

of this divine carving.

- Over the course of a year,

the shadow moves across the entire bas-relief,

essentially functioning as a calendar.

- [Narrator] The movement of this shadow

mimics the encrypted tug of war

pendulating from side to side throughout the year.

- The cosmology is played out

through the westward orientation of the temple.

- Many civilizations have drawn connections

between astronomical observations

and their religious beliefs, believing that in part,

their lives were governed by the celestial.

This stems from a basic human need

to understand the universe and our place in it.

- [Narrator] Some scholars suggest

that Angkor Wat is not only a temple

dedicated to Vishnu and cosmic order,

but was also intended to be a tomb for its commissioner

and ruler, King's Suryavaman II.

- What was the king's true intention for the structure?

Was it merely a temple or was it a mausoleum?

(bright music)

- As far as we know, the king was never buried there.

We believe that he was killed on a battle site far away.

- [Narrator] Although King Suryavaman II's temple

still stands, his death precipitated the decline

of his dynasty and the Khmer Empire.

- So not long after Angkor Wat was built

and the king died in battle, we think,

the Khmer regime fell

and the new power in place was Buddhist,

and so it was converted into a Buddhist structure.

- This is a rare example

of religious conversion in monumental architecture.

- But 300 years later after it was built,

Angkor Wat would be abandoned.

Now, a lot of this had to do with catastrophic flooding,

which was in many ways a legacy of the intricate

and sophisticated water system that had been developed

by the people during the 12th century.

- The extreme weather events

that occurred at Angkor Wat overwhelmed that system.

When we desig buildings,

we base our designs on climactic data, historic data

that our structures will experience, its probability.

Angkor Wat was designed at a certain period in time

for a particular experience.

In the 15th century,

there would be these extreme monsoon seasons followed

by these extreme droughts, and the system couldn't keep up.

- Ironically, this city's connection to water would be one

of the reasons for its monumental downfall.

- Angkor itself was destroyed by flooding.

- [Narrator] Though the temple is visited

and preserved by local monks

and Khmer people through time,

its full splendor is not understood

by the modern Western world

until Henri Mouhot's fortuitous encounter in 1860,

which sparks a new era

of intense study on the structural design.

By the 1990s, evidence of an astral motive grows stronger

as a series of researchers identify calculations

that reflect the cosmic clock.

Using the Khmer unit of measurement

known as the Cambodian qubit or HNt,

experts have postulated

that the temple's dimensions further encode

an advanced understanding of time and space.

For example, the dimensions

of the temple's highest terrace are believed

to equal 365 HNt, corresponding to the number

of days in a year.

The base of the central tower measures 91 HNt,

aligning with the 91 days that separate

a solstice from an equinox.

Additionally, within the temple's central structure,

the distance between each step is 12 HNt,

reflecting the 12 lunar cycles that make up a year.

These are only a few of the dozens of dimensions

that seem to correlate with celestial cycles

and no doubt there are many more still to be discovered.

- Despite centuries of studies,

Angkor Wat continues to guard its many secrets.

- [Narrator] The Khmer are not the only

nor even the first civilization

to achieve this celestial union with architecture.

On the other side of the globe,

nearly 16,000 kilometers away,

another ancient structure

with hidden secrets is similarly imbued

with solar significance.

- This pyramid appears relatively simple at first glance,

but in actuality it's been found to harbor hidden chambers,

human remains,

and possibly an intended portal to another realm.

- [Narrator] Nestled in the lush heart

of Mexico's Yucatan Peninsula is a city

that offers a glimpse into a world long past.

- Chichen Itza was a thriving metropolis.

It was famous at the time that it was first encountered

by Europeans for being this sophisticated urban culture.

It was the center of Mayan culture at the time.

- [Narrator] This ruinous site

is one of the seven wanders of the modern world,

and its centerpiece is the pyramid of Kukulcan,

otherwise known as El Castillo.

Its simple facade guards secrets

that date back for over a millennia.

- Not unlike the pyramids of Egypt,

historians, archeologists are still puzzling

to this day about the particular function of this pyramid.

- [Narrator] Researchers have discovered

strange numerical, visual and even acoustic features

within the pyramid's architecture

that seemingly linked the structure to the Maya calendar.

- Could this have been an observatory

or a site of celestial ceremonies?

How do the skies above facilitate its mystical purposes

and what other mysteries lie beneath its stone exterior?

(dramatic music)

- Often referred to as the Greeks of American civilization,

the Mayans were an incredibly diverse

and advanced civilization.

- They left behind an extraordinary legacy

in terms of monumental architecture.

But at the time,

they were also a large thriving economic, social

and political empire.

- These famous Mesoamerican ruins were once home

to a lively city, founded by Maya settlers as early

as the fifth century CE.

By the 10th century, Chichen Itza had grown to be one

of the biggest cities in Mayan history.

During this era, somewhere between the 10th

and 12th centuries,

construction began on a grand four-sided pyramid

dedicated to their feathered serpent god, Kukulcan.

- The pyramid is dedicated

to the most powerful of the Mayan gods.

He was a feathered serpent kind of creature.

He embodied the cosmos.

He could move between the realms

of existence from this world to the world

of the deities down to the underworld.

- [Narrator] Kukulcan was one of the most revered deities

in the Maya Pantheon, which included

over 200 gods and goddesses.

Kukulcan was believed to govern the cycles of the cosmos

and oversee the seasonal rhythms of growth and decay.

- We can see that with Kukulcan being the feathered serpent,

that there was a great reverence on flight on the air

and the space above, this is that divine space, the space

that they would reach up to that they could build up to,

but could not engage in themselves.

Because as men, we don't fly.

- [Narrator] At a soaring 30 meters,

The temple of Kukulcan attempted to close the gap

between humans and the heavens.

- Having been to El Castillo in Chichen Itza,

it's really quite an impressive pyramid.

It's situated by itself on a plane,

so it looks very impressive and imposing.

- [Narrator] When the Spanish arrived in the new world

and saw this towering fortresslike structure,

they called it El Castillo, which means the castle.

- When the Spanish got there, this would've been, you know,

something that's really out of context for them.

There wouldn't be anything in Spain

or the rest of the world that they've been to

that would really compare to these types of structures.

- While this monument may appear unassuming,

you have to consider at what time it was being constructed

and what materials were available to them.

- The structures themselves are made of the local limestone.

There is no other material in the Yucatan

to use to construct, so all of their buildings

are actually constructed

of a relatively porous limestone material.

- [Narrator] El Castillo's simple design is striking.

The square base measures over 55 meters

on each symmetrical side.

Four uniform staircases meet at the pinnacle,

a rectangular sanctuary with a flat stone roof

that contains four entrances and three inner rooms.

- The structure is impressively well proportioned

from its foundation to its temple.

So how did they achieve such a masterful feat

with incredibly limited tools?

- El Castillo's a stepped pyramid

where we've actually built terraces of rock up

to produce the pyramid shape.

That's a very stable structure.

It's a very easy construction methodology.

Again, you can use simple incline planes

to push rocks up ramps and place them

and then continue to build your pyramid

as you place layer and layer and layer.

- [Narrator] This temple dedicated to Kukulcan

dominates the landscape.

However, many believe this structure

to be more than just a massive monument of worship.

- The Mayans developed a very sophisticated approach

to astronomy that led to the development

of these multiple calendrical systems, which were used

to help them not only with their religious observances,

but with organizing the rotation of crops,

harvesting and other economic activities.

- The Mayan calendar has similarities

to our modern calendar, a 365 day year, for example,

but it was also a lot more complex,

combining multiple cycles

to track time with remarkable accuracy.

This profound comprehension

of cosmic cycles is physically embodied

in many Maya structures, including the pyramid of Kukulcan.

This monument has 91 steps on all four sides,

and when added together with a temple landing on top,

these equal 365, one step for each day of the year.

91 is also the number of days

between each annual quarter marked by the equinoxes

and solstices,

and each side of the structure has 52 decorative panels,

which is the exact number

of years in the Mayan calendar cycle.

- In essence,

this pyramid embodies the Mayan calendar itself.

- But what was the ultimate purpose

for this cosmic coordination?

Could aligning their architecture

with the eternal coil of time,

facilitate a deeper connection with their deities?

- [Narrator] The meticulous design matched

with the porous properties at the site's limestone slabs

give rise to a fascinating occurrence

at the foot of the pyramid.

- When you clap your hands at the base of the pyramid,

the sound bounces off different stone surfaces.

(hands clapping)

And it almost mimics the chirp of a bird.

- [Narrator] This fleeting echo strikingly resembles

the warble of the quetzal bird.

(quetzal bird chirping)

- This is a sacred bird that still exists to this day.

Its distinctive look of green feathers with a red body.

It evoked for them similar elements to the image

of the feathered serpent deity, Kukulcan.

- Was this effect intentional?

How could the Maya have engineered such an acoustic marvel?

- I would find it very surprising if the echo sounds

produced by El Castillo were intentional.

I think it would've been very difficult

or almost impossible for the people of that time to be able

to recognize these audio effects.

I think it probably arose simply as a result

of the technology used to build the structure

and not a direct intent.

- When we think about the marvels of this engineering,

we do have to wonder what is intentional and what is not.

But another interesting effect

is actually the use of light.

- [Narrator] During the equinoxes,

when day and night stand in perfect balance,

a mysterious shadow seems to slither down the balustrade.

- The way the light shines in at midday,

it can look like a serpent

slowly coming down the walls.

- [Narrator] As the sun moves through the sky,

the undulating shadow seems to align perfectly

with a serpent skull at the base of the steps.

It's as if Kukulcan himself is descending

from the higher realm to bless his worshipers.

While the pyramid's exterior dazzles with divine symbolism,

its interior guards an age old secret.

In the early 1900s, the ruins of Chichen Itza

were largely covered by dense jungle.

Much of its architecture obscured.

In the 1920s and 30s,

explorers began clearing the vegetation,

slowly revealing its grandeur

and intricate design, including a hidden passage

leading to a sealed chamber.

As the door to this room creaks open,

rare artifacts are revealed.

- One of the most interesting discoveries

was a red jaguar throne.

The jaguar itself is associated with power and authority.

The color red is associated with birth

and sacrifice and death in the Mayan tradition.

- [Narrator] Beyond the treasures found

in what has become known as the hall of offerings,

in an adjoining chamber,

archeologists make a startling discovery.

- There's a room that's now been named

the chamber of sacrifice because they discovered in it

the presence of human bones.

- Could they have been sacrificial offerings

and what prompted their concealment

deep within this ancient structure?

- [Narrator] Further investigation reveals

that these hidden chambers,

are part of a much older pyramid

that lies beneath the current structure.

The ancient temple dates to between 800 CE and 1000 CE

and is approximately 17 meters high.

About half the size of El Castillo.

The Maya often built new temples over older ones

creating layers of history.

It's not until 2016, however,

that technological advancements adds

yet another fascinating layer to this tale.

When digital mapping detects the presence

of a third building at the site's core,

a 10 meter tall pyramid nestled inside the other two.

Analysis has since dated this interior pyramid

to as early as 550 CE,

approximately half a millennia older

than the exterior we see today.

- It's actually a pyramid

built on a pyramid, built on a pyramid.

- So essentially it's like a Russian doll of pyramids.

- [Narrator] In capturing the skeleton of this building,

digital mapping has also revealed the earthen foundations

upon which it's built.

This thousand year old stone shrine rests on a layer

of limestone bedrock around five meters thick,

below which is not compact earth,

but a cavernous 20 meter deep well believed to be a cenote.

(bright music)

- The Yucatan is really interesting

because it doesn't have above ground water flow

and all the water actually flows

through underground cave systems.

Periodically in the Yucatan, some of the caves collapse

and they produce these basically very large holes

in the ground called cenotes.

- Today, the Yucatan Peninsula is known

as the cenote capital of the world.

There are over 6,000 there,

and this helps us reflect on the Itza people

who once lived there and built the pyramid.

These cenotes were critical reservoirs

that they relied upon for daily use,

but they were also critical to the performance of rituals.

- [Narrator] The city of Chichen Itza

is built in the proximity of four cenotes.

The most northern of these is known as the Sacred Cenote

used by the Mayan as a site of ritual

and sacrifice to the gods.

Over the centuries valuables such as jade, ceramics, gold,

and even human remains have been recovered from the depths

of this revered site.

- Any kind of crevice like this can be a gateway

to another reality.

So these are portals

and for the Itza, these were portals that led to Xibalba,

which is their underworld.

- [Narrator] To grasp the significance of this discovery

and whether the Maya knew of the cenote's existence,

researchers must uncover an entryway

connecting the pyramid to the cavern below.

If they succeed, it may reveal

that Kukulcan is not merely a path of ascension

to the heavens, but also a portal to the cross section

of dimensions, or in other words, the axis mundi.

- The axis mundi is a concept we find

in a lot of ancient cultures.

It's Latin for the axis of the world, the center place

of the world where different elements

of the cosmos come together.

Often that's sky and earth, sometimes it's sky, earth

and underworld, but it's the nexus that joins the universe.

- [Narrator] Could it be that the pyramid of Kukulcan,

designed in dimensions guided by the stars,

serves as the Mayas axis mundi?

(peaceful music)

Today over a millennia

after its original construction, the pyramid of Kukulcan

and the surrounding city of Chichen Itza have become

one of the most visited destinations in the world.

- I think the pyramid teaches us that there's still

so much we don't understand about previous societies.

- [Narrator] Many wonder what secrets remain enshrined

in this limestone sanctuary and do the waters below hold

the answers previously thought to be lost to time?

Guarding yet another cosmic enigma on the opposite edge

of the Atlantic, an unassuming artificial mound

rises from the earth.

Its form standing strong for over 5,000 years.

- This amazing structure predates Stonehenge, the temples

of ancient Greece, and even the Pyramids of Giza.

- [Narrator] Known today as Newgrange,

this monument retains an air of mystery in modern times.

- The construction of Newgrange

required a sophisticated understanding of both astronomy

and architecture, making it one of the most remarkable feats

of the ancient world.

- [Narrator] The architectural elements

of this ancient edifice seems centuries ahead of their time,

yet so much remains unknown about the neolithic visionaries

who created it.

- Who were the architects behind this ancient wonder?

How did they make such accurate astronomical alignments

with prehistoric tools

and what inspired them to forge a connection

with the patterns of the sun?

(dramatic music)

- [Narrator] Situated along the bend

In Ireland's River Boyne

is the UNESCO heritage complex of Brú na Bóinne.

Here, a collection of at least 90 monuments

spread across eight square kilometers

hold the largest collection

of megalithic art in all of Europe.

Dominating this stone spectacle landscape is Newgrange,

a large passage tomb sheathed by a cairn.

- A passage tomb is a burial chamber covered by earth,

which can be accessed by a narrow passageway.

Some are covered by cairns, which are piles

of stones usually erected as a memorial or marker.

These are quite common in neolithic times

and are typically found across Western Europe.

- [Narrator] There are many examples

of this type of construction,

but few rival Newgrange.

Comprised of an astounding 200,000 tons of material,

the mound measures 13 meters high and 85 meters in diameter.

- Although Newgrange is not large to us,

in comparison to modern structures,

to our neolithic ancestors,

it was likely enormous.

- It's massive,

and it does make you wonder who built this?

How did they build this,

and most importantly, why did they build it?

- [Narrator] Using radiocarbon dating,

researchers have determined

that Newgrange was erected in or around 3200 BCE.

- We don't actually know a lot about the people

who constructed this complex.

They were likely farmers who raised livestock

and grew crops in the surrounding region.

- We think they were an advanced society

that had a refined knowledge of stonework

and architectural design.

- [Narrator] From a bird's eye view,

Newgrange camouflages itself.

It's roof sowed with green grass.

From the ground, however,

it's imposing exterior is difficult to miss.

Faced with contrasting cobblestones of white quartz

and black granite.

- Were these ancient planners trying

to illuminate certain parts of the building?

- [Narrator] The answer to this question

might never be known.

The facade we see at Newgrange today is the result

of a 20th century restoration.

While the cobble stones used were discovered on site,

and there is evidence that contrasting stones

were part of the original design, the accuracy

of their placement remains a topic of debate.

- The challenge in reconstruction

is how do we recreate the facade

of a neolithic structure when we're not even entirely sure

what it might have looked like in its original form.

- [Narrator] The dome itself is a pile of thousands

of water rolled pebbles pulled from the depths

of a nearby pond, each measuring up

to 22 centimeters in length.

The hundreds of larger slabs that form the structure's bones

and perimeter, are predominantly crafted from greywacke,

a type of sandstone, some pieces measuring upwards

of four meters in length.

Yet these formidable boulders

are not so easily sourced as the pebbles.

- The megaliths, the large stones that were used

to build Newgrange were hauled

from maybe 50 kilometers away.

- Some theories suggest the stones may have been transported

over land using wooden rollers or a sled.

Then there are other theories

that they may have been floated down the coastline

and transported by water up the river.

Either way, this would've been a monumental task.

- [Narrator] This incredible task suggests

that the ancient architects could have had a labor pool

numbering in the hundreds.

Even with so many hands, it would've been a task

that took decades to complete.

- This was a time when metal hadn't been fully developed,

so the workforce's tools were made entirely

of wood, stone and bone.

- Building of it must have taken they estimate

as long as 70 years or more to build,

which would've been more than one lifetime

for many of the people who were involved in this building,

it meant that society had to organize over the generations

to continue its work so clearly

as purpose from the start resonated long term in the culture

and was considered important to complete.

- The prehistoric prestige

of this site may have been etched

into the very stones that support its walls.

Among the hundreds of greywacke rocks

that line the building's edge and interior,

75 are arranged with some of the most cohesive

artistic compositions of neolithic times, the most prominent

of which can be seen on the tomb's entry stone,

boldly marked with a large triple spiral design.

- What do these carvings signify?

Do they mark a boundary between two realms?

Are they an abstract representation of ancient beliefs,

or could they be the mark of a dynasty?

- Since we don't really have any written records

of this society, we have to rely on artifacts.

- Venturing inward, cryptic carvings

mark the narrow walls.

- The passage into the structure is long and claustrophobic,

and when you get to the center of the tomb,

you're confronted by three chambers.

- [Narrator] The entire floor plan mimics

the shape of a cruciform.

Its most inner region protected by a vaulted ceiling

that has remarkably stood the test of time.

- In some ways, the passage

and the chambers within the building are a bit rough,

but it's amazing the technology

that went into constructing this thing in the very back

of the passage where the chambers, the burial chambers are.

If you look up, there's a high corbel dome,

and that dome has not leaked in 5,000 years,

more than 5,000 years.

- [Narrator] It's beneath these corbel stones

in the tomb's quiet chambers,

where the mysteries of Newgrange begin to unfold.

After thousands of years in ruin beneath layers of earth

and vegetation, Newgrange becomes a site

of intense intrigue when a local farmer rediscovers

its concealed entrance in 1699.

it will be another two and a half centuries

before the first thorough archeological excavation

is conducted by Michael J. O'Kelly

in the 1960s and 70s.

As his team clears the corridor and chambers,

they uncover large stone basins believed

to once cradle the ashes of the dead.

Beneath the floor, a large pit is dug in the central chamber

and a discovery is made

that confirms Newgrange is not just a site of ceremony,

but also a tomb.

- They discovered 23 components of human remains,

which likely belonged to five people.

Is this a collective grave, and if so, for whom?

- [Narrator] Recent DNA analysis

of the recovered bone samples from a neolithic man

identified as NG10 provides startling insight.

A genetic profile marks him as the offspring

of an incestuous union within this ancient community.

- It's likely that his parents were siblings

or were looking at a parent and a child.

This man may have been part of a dynasty that was concerned

with preserving the royal bloodline.

- [Narrator] This practice has been observed

in other dynastic societies,

including the pharaohs of ancient Egypt.

The earthly importance of those buried

and the ingenuity

of the ancient architects were further highlighted

in December, 1967.

While working in the chamber, O' Kelly bore witness

to a surprising spectacle firsthand, a magical glimmer

of natural light streaming from a crevice

above the tomb's entrance.

- There was a roof box, which was carved out

above the entrance to the passageway,

which allowed the sun on the winter solstice

to enter right into the very back chamber.

- This unique display occurs only once annually,

on the shortest day of the year.

- The winter solstice.

This is the longest period of time that the sun is absent.

- [Narrator] Once a year at the dawn of the winter solstice

for 17 minutes, the sun illuminates the heart of Newgrange,

flooding the central alcove of ancestral ashes

before retreating to the vast skies above.

- Greatest spectacle was for the people inside,

deep inside the chamber,

but there was another spectacle outside.

In Newgrange, the entranceway was covered with white stones

that would reflect the pink of the rising sun

on the winter solstice.

- It's astonishing to imagine prehistoric people

planning and building such a structure

that aligns with the stars.

- With the advent of the Bronze Age,

Newgrange largely falls out of use as a wave

of settlers overtake the native population.

Yet its celestial significance lingers on.

The new communities erect additional menhires

around the mound,

forming what is now known as the Great Circle.

Continuing the interplay of structure and sun,

it casts shadows across the site.

The shade of its tallest pillar, touching the middle

of the famously carved entry curve

on the day of the winter solstice.

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- In Britain, we're famous for our stone circles,

and Stonehenge is always the number one visited site,

but it's not just about Stonehenge.

There are so many other sites that predate it.

And Newgrange is a fantastic example.

- [Narrator] Due to the gradual shifting of Earth's axis,

our astronomical clock runs four minutes faster

than that of Newgrange's neolithic engineers.

Yet still, people visit every year

to watch the solstice sunrise herald the dawn

of a new phase.

From the haunting neolithic stone monuments of Ireland

to the awe-inspiring Mesoamerican pyramids of Mexico

and the breathtakingly ornate temples of Cambodia,

these ancient wonders stand through time

as architectural reflections of the cosmos.

Though modern investigations have begun

to unravel their mysteries,

countless secrets remain veiled in the midst of time,

just waiting for the bold

and curious to uncover even more of the hidden secrets

of these ancient structures.

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