Original subtitles

Magnificent temples

carved from a single massive rock.

A megalithic fortress

encoded with a mysterious hidden language.

And mystifying stone tombs

that may have been created to contain a creature

of monstrous proportions.

Some of the greatest mysteries on our planet can be found

in the ruins of ancient structures

that are often described as nothing short of extraordinary.

All around us, we find walls

made of massive interlocking stones,

sacred temples constructed with complex geometry,

and colossal architectural masterpieces

that rival or even surpass what we can create today.

How did the builders of these structures achieve

such seemingly impossible feats of engineering

without the use of modern technology?

Well, that is what we'll try and find out.

China.

With over 4,000 years of recorded history,

it is the oldest continuous civilization in the world.

Its rich culture has been shaped

by powerful dynasties and countless wars

and unrivaled feats of engineering

that are truly a wonder to behold.

But of all its dazzling constructions,

none is more iconic or monumental

than the Great Wall.

The Great Wall of China

is now classified as one of

the Seven New Great Wonders of the World.

We think of the Great Wall as

this one thing that the tourists visit near Beijing

which is, like, extremely refined,

sophisticated architecture,

but actually, it consists of many walls

stitched together over 2,000 years.

The length of the wall, until recently,

was thought to be about 2,000 to 5,000 miles.

Now we know it's 13,000 miles.

Okay, that's half the circumference of the Earth.

This is by far the largest human-made structure

on the entire planet, by far.

It's amazing. It's phenomenal.

At the same time,

you have to wonder, what the hell were they thinking?

We certainly know that the wall

functions as a very, very long castle.

There have been times it's been attacked

and the people on the wall have held those attackers off.

Originally, in the 220s BC...

the first emperor of China, the man called Ying Zheng,

decided to stitch together the little walls

that connected the little kingdoms

to hold out barbarians in the north

who are coming across his border.

But different dynasties had different walls.

You got four or five different

nomad groups that are various threats.

As time goes on,

it extends further and further out

towards the west,

over by this remote part of the desert.

And sometimes it uses gravel and reeds and mud,

which is also rammed down and closely compacted.

Sometimes it even uses wood.

Eventually,

the Ming Wall, the one that was built

in the 14th century, um,

that uses stone and sometimes brick.

And sometimes it's 50 feet tall,

sometimes it's 30 feet tall, sometimes it's ten feet tall.

You put this huge amount of manpower

into creating this really impressive edifice,

and if that scares your enemies away

before you even have to fight them, then you've already won.

The walls were certainly significant.

We think of them as military operations.

But the most important purpose, I think, is economic.

That they could funnel the trade that was coming

in and out of China through these gates.

You could monitor the goods. You could tax them.

And they also controlled

the human populations that sort of came through.

So these gates served as a hybrid

military, economic project.

And, of course, it worked, but it also, like, didn't work.

In the 13th century,

Genghis Khan and his Mongolian hordes

famously broke through these legendary defenses

and actually took control of China.

Rebel forces overthrew the Mongols in 1368

and established the Ming dynasty.

For nearly 300 years, the Mings built

and reinforced over 5,000 miles of even more sophisticated walls

until the dynasty collapsed in 1644.

What we see today is a construction effort

that spanned two millennia and largely remains

one of Earth's greatest man-made mysteries.

In archaeology,

we have a method or a strategy

for studying how much investment goes into architecture.

It's called the study of man-days.

How long would it take me to do this?

No one has yet calculated

the man-days required to build the Great Wall of China.

The problem is that you can't get inside

all the sections of the Great Wall to understand

just what they encountered

trying to build over mountain passes or ridges,

across valleys and these kinds of things.

The investment and the resources are

so enormous, it's almost unimaginable.

While some believe that a construction effort

of this scale would easily take millions of people,

the actual size of the Great Wall's workforce

remains unknown.

Although the structure has become a symbol

of China's strength and ingenuity,

it's likely those tasked with the construction

were living in a grim reality.

I would say that most of the wall

was constructed through forced labor.

Being sent to the wall was a punishment.

It would just say on the statute books "qiáng,"

which means "wall," and that's where the men

were sent to carry bricks and ram earth.

But there was a punishment for female criminals, as well.

It said "sent to pound rice."

And for centuries, no one really knew what that meant,

but it turns out that the bricks in the wall

need cement to hold them together.

And these armies of female convicts were sent

to create this sticky rice soup

that creates a really powerful, strong cement.

And so, these people are basically being exiled

in the middle of nowhere,

and the wall for them is a kind of prison.

The workers were essentially worked

to death in many cases, and there are reports

of a lot of these people dying

while they were building the wall.

There are folk tales,

um, that have been recorded about people

who expired being buried under the wall

or their bodies being used to build the wall itself,

which is quite a macabre thought.

And we can't really look for these bodies

or the remnants of the bodies.

Were dead bodies really used

in the construction of the Great Wall of China?

Some estimate that upwards of a million workers

lost their lives,

so it remains a chilling possibility.

And while there are countless unanswered questions

about the making of this engineering marvel,

Chinese researchers have begun using modern technology

to try to solve the mystery

of this wonder of the world.

In 2018, researchers from Tianjin University

decided to do a full-scale drone-mapped survey

of the Ming dynasty portion of the Great Wall.

And what they found took a lot of people by surprise.

They were able to get a comprehensive view of areas

that people aren't normally able to access,

and they discovered these doors--

they're effectively holes-- in the wall

that were used at various portions

for troops to surprise enemies

by suddenly appearing through the wall.

They were gates, basically, that nobody knew about.

There were more than 200 of them hiding in plain sight.

It turns out that the wall

was not just some solid monolith.

There were actually passageways,

these secret doors that were totally unexpected.

China has only recently

come to really start to explore itself historically,

archaeologically, scientifically.

We haven't known a lot about why the Great Wall was built.

And I can tell you from firsthand experience,

it is simply impossible

to access many areas of the Great Wall.

And you have to remember,

we can't see underneath the wall.

We can't see if there were people

who died in the construction and were thrown in the fill.

We can't see if there were settlements that were built

and then the wall covered them.

What are the different features of the wall?

We just don't know these things.

So I think the mysteries are gonna continue to unfold

over the course of the next several lifetimes.

In the shadow of the Great Pyramids

sits a monumental ancient landscape

of countless architectural mysteries

that continue to defy understanding.

And just northwest of the Pyramid of Djoser,

the oldest pyramid in Egypt,

lies one of the most baffling

archaeological sites ever discovered:

the Serapeum of Saqqara.

In 1850,

French archaeologist Auguste Mariette

finds a head of a sphinx in the sand

and decides to dig under it.

And as they excavate,

they find staircases down to some catacombs.

And when they go inside,

there's a burial ground with chambers,

doorways, corridors, and most intriguingly,

there are around 60 tombs

and 24 giant sarcophagi.

These sarcophagi are unusual because they are so huge

and they are clearly not human tombs.

This place was built around 1400 BC

by the Pharaoh Amenhotep III,

who very much revolutionized Egypt,

and it seems to have been used right up until about 30 BC,

but the sheer scale and precision of the sarcophagi

suggests that they did have some

importance that isn't just clear to the eye.

The Serapeum of Saqqara

is based around two large corridors,

each with offshoot rooms

where the sarcophagi were housed.

This is what we would call the coffins.

And the sarcophagi in the Serapeum

are absolutely huge.

Ten-foot-wide, 13-foot-long, each with its own lid

and weighing around 60 to 70 tons.

Moreover, what makes each sarcophagus really unusual

is that they are built of one piece of solid granite.

They have been brought down into the Serapeum as one piece.

It's simply remarkable.

Sarcophagi that you might find

in royal tombs in the Valley of the Kings or in pyramids

are rectangular boxes,

roughly human-body-shaped and then a little bit larger.

These sarcophagi in the Serapeum

were more like the size of a small building,

which prompts us into thinking, you know,

how on earth did the Egyptians even go about

cutting pieces of stone like this

but also maneuvering them into position?

To get these huge sarcophagi into the burial vaults,

they have to travel a long way in quite a confined space.

And the fact is that we don't know

precisely how the Egyptians did this.

What could possibly be entombed

in a ten-by-13-foot coffin that weighs 70 tons?

Well, some believe the answer lies with a large animal

the ancient Egyptians considered sacred,

known as an Apis bull.

The Apis bull was a real-life bull,

a-a real animal, identified by the priests

according to particular markings.

It had to have the right combination

of black and white markings, and that would be

the giveaway that, in fact, this was the Apis bull,

which was believed to be a manifestation

of the spirit of the god Ptah.

And Ptah was a creator god

and the most important god in the capital city of Memphis.

And once the Apis bull was identified,

it would be taken to the Temple of Ptah

and looked after and treated as if it were a god.

And at the time the bull died,

they would have been given a full ceremonial burial

comparable to the funeral of a pharaoh.

While we do know Apis bulls

were buried in ancient Egypt,

were the giant sarcophagi in the Serapeum of Saqqara

specifically designed to inter the mummies

of these holy creatures?

When the catacombs were first being explored,

the remains of a few bulls were found mummified

in a slightly sort of unexpected way,

in that the bodies appear to have been broken up

and gathered together in a kind of bundle.

But because most of the sarcophagi

have been found to be empty,

there are questions about whether or not

they really were the sarcophagi for mummified bulls.

The evidence is a bit thin on the ground.

It's very possible that the sarcophagi were used

to house the Apis bulls themselves.

But as usual with things in ancient Egypt,

there's both evidence for and against.

But we don't have a lot of the ancient skeletal remains

resulting from that, and so of course it's enormous fun

to speculate who these tombs might have been created for,

given their absolute vast size and proportion.

What purpose did these

enormous stone vessels truly serve?

Were they actual tombs?

While a lack of physical remains

has certainly led to various theories,

the most tantalizing hypothesis

revolves around an ancient race of giants.

When you look back

and go into the old Arabian records

and myths and legends,

you find stories from the book Akhbar al-zaman,

which was written about a thousand years ago.

It detailed all these giant, godlike beings

coming from the land of Ad or Adam,

and arriving in Egypt and building the pyramids.

We have the first pyramid in Egypt being built at Saqqara,

and we have these giant sarcophagi.

Some people have suggested that these could have housed

human giants.

And you find all these stories of these giant pharaohs.

And there are lots of images that have been recorded

on many of the walls of the tombs and temples of Egypt.

Some of them look like they're depicting giants.

I mean, you kind of have to admit that.

So I find this really, really compelling.

Was the Serapeum once

a burial ground for giants?

It's a fascinating idea to entertain,

but the truth is the answers to how and why

these immovable containers were created

remains lost to the sands of time.

If there is one

really great enduring mystery about the Serapeum, it's really

whether, in fact, we have found everything

of the Serapeum, or if one day,

a bit of archaeology could lead us to new chambers

with everything that that might bring.

Was there supposed to be

something else there that we don't know about?

And so, it's making us

ask questions about

this period of ancient Egyptian history

that's not very well known.

It's hard to imagine just how much time and effort

went into constructing the giant sarcophagi at Saqqara.

And perhaps the bigger question is: Why?

Like in the case of another impossible structure

found in India.

It's an enormous temple

carved from a single piece of stone.

Just outside the city of Aurangabad

lies the Ellora Caves,

a series of rock-cut temples, shrines and monasteries

carved out of a massive basalt cliff

stretching for more than a mile.

Constructed by a series of dynasties that ruled India

between the sixth and tenth century AD,

this extraordinary complex is an unparalleled monument

to the diverse spirituality of India.

The Ellora Caves is a religious site

that are a series of cave temples in western India.

And it is one of the most breathtaking structures

in all of South Asia, if not the world.

It is comprised of 34 different caves.

32 of the caves are proper cave temples,

while two of them are rock-cut,

freestanding temples.

17 of them are Hindu, 12 are Buddhist,

and five are Jain.

This particular part of India

had many important trade routes,

and the rulers there also had a great diversity of religions.

It was the duty of the king to make everyone feel welcome.

While the Ellora Caves symbolize

an era of religious harmony in India,

their beauty and precision

also represent a true mystery of ancient engineering.

And the site's most baffling construction

is the Kailasa Temple.

Built in the eighth century AD

and spanning an area of about 300 feet long,

175 feet wide and 100 feet tall,

it's the largest monolithic temple in the world.

For Kailasa Temple, to replicate it today

would be nigh to impossible.

Part of the mystery is trying to reverse engineer

what they did and how they made this.

So, normally, you build a building

by starting with a ground plan and building up.

Here, these are rock-cut,

which means you start from the top

and you work your way down, chiseling the material out

to make it look like it was built from the bottom up.

So, basically, you're building these things,

in a way, upside down.

And the skill of producing this and the geometry,

it doesn't exist anymore today.

We don't have any way to understand exactly

how they were doing this.

So you have to scoop out the rocks

and then build the temple.

It's like a piece of a sculpture.

And there has to be a blueprint in order to carve such a temple.

But there has been no evidence of finding a blueprint

or even mentioning that there was a blueprint.

So, is it mentally imagined?

Or maybe they used a small replica,

like a model of a temple that they had on the side.

We don't know.

There are not any written documents.

So we are totally baffled. It's an enigmatic temple.

Three million cubic square feet

was the amount of stone that was removed.

And that is another of the big mysteries here.

Where did it go? How did they move it?

It's still an enigma because just to be there,

to walk in that space--

you have a multistory building

of immaculate beauty and complexity

that is a single piece of stone.

The curvatures and the sculptural tableau

are so intricate, so beautiful and so profound.

It's hard to conceive that anyone could do it,

even with modern technology.

It's estimated that 200,000 tons of stone

were removed to create Kailasa Temple,

the equivalent of two U.S. Navy aircraft carriers.

And what makes this exquisite structure

even more extraordinary

is how quickly it was constructed.

Kailasa Temple was allegedly built

in less than 20 years,

which has left a lot of people wondering how--

by what means or methods they accomplished such a feat.

And especially if we're thinking that the site was built

about 1,400 years ago, this is doubly impressive.

So there have been certain hypotheses that there were

certain tools that vibrated at certain frequencies

that were used to break down the rock.

Magnetism might have been used.

But there's no hard evidence for any of these building methods

and no record of how

these methods were deployed on the site.

Could some kind of lost technology

have been used in the temple's construction?

Well, it's certainly a possibility,

but legend has it that there may have been

some supernatural assistance at the Ellora Caves,

and according to local folklore, secrets may still be hiding

deep inside the mountain.

There is this 13th-century work

known as the Leela Charitra

that tells the story of the visit of Chakradhara,

this great Hindu sage, into the vicinity of Ellora.

And he's traveling there with his disciples,

and they need to find refuge for the night.

So they go and spend the night at the caves of Ellora.

They start hearing strange voices emerging

from out of the beautiful sculptures that surround them.

And some of them start having odd visions,

and one of the disciples

turns to Chakradhara

and asks, "How could these possibly be built?

What is this structure?"

And the master says, "This whole mountain is filled

with hidden chambers and all kinds of hidden tunnels,

and no one knows their entrances or their exits."

And so, this is probably the story of the start

that there are all kinds of hidden caves,

and that lends to a lot of later speculation, as well.

There are legends that the Kailasa Temple

was constructed by the gods themselves

or certainly that they had a hand in its construction.

And this therefore suggests the possibility

that a lost technology was actually involved.

So, whatever way you look at this,

this is an extraordinary achievement for humanity

and one that we still cannot explain to this day.

Could a secret chamber inside the mountain

hold the answers to how and why the Ellora Caves were created?

If so, its discovery could potentially rewrite

much of what we know about ancient engineering.

Not unlike another baffling stone structure in Indonesia,

the largest Buddhist temple in the world,

that was mysteriously built and abandoned

more than 500 years ago.

Dominating the skyline is

Mount Merapi, Indonesia's most active volcano,

standing like an ancient guardian

above miles of dense, misty jungle.

And in 1814, when this island nation

was part of the Dutch East Indies,

Javanese locals spoke of a strange location

hidden in the jungle

they called the Mountain of a Thousand Statues.

The British had control

of the Dutch East Indies, and their governor,

Thomas Stamford Raffles,

was on this inspection tour in what is now Java.

And the locals said to him,

"There's a few statues up that hill."

So he sent some engineers to check.

The engineers came back, and they said,

"They're not just a few statues up that hill.

They're all linked together. There's some kind of complex."

And it's not a hill.

The hill is the complex.

They had to clear away 200 trees and a load of ash from the soil

before it started to reveal itself

as this nine-stepped place of worship.

And they slowly revealed Borobudur,

this massive Buddhist temple in the middle of nowhere.

The temple covers an area of 25,000 square feet,

and it would technically

be the largest Buddhist temple in the world.

Borobudur is designed as a mandala.

A mandala is a diagram of squares and circles

that Buddhist monks would use for meditation practices.

There are these square terraces, and they represent

the transition from the troubled daily life

to nirvana, which is a life

freed and blessed from any types of problems.

This building is a philosophy expressed in architecture.

Towering at about 115 feet

is the site of Borobudur.

It's composed of nine stacked tiers or nine stories.

It has over 500 Buddha statues

and 2,000 relief panels

that tell the story of the Buddha

and his progress towards enlightenment.

When visitors are going through the site,

they are effectively going through a path to enlightenment

that's laid out in stone.

Actual records of Borobudur's construction

have never been found, but most historians believe

this remarkable structure was built

around the ninth century AD by the Shailendra dynasty,

a powerful family that once ruled Indonesia

and established Buddhism in the region.

And while much of the site's origin is unknown,

many believe Borobudur's greatest mystery

is that after centuries of use, this awe-inspiring site

was left completely abandoned.

Sometime in the 15th century, everything is abandoned.

No one knows exactly why.

It could have been changes of military power.

Could have been changes of economic power.

Could have been the mountain started rumbling

and people got nervous.

It could have been any number of possible reasons.

But it is quite astonishing.

They moved out, and they moved

to other places on the Java Island,

and Borobudur was just left to the jungle.

That's very mysterious.

Why was such an impressive

Buddhist temple abandoned?

While some historians believe it was due to a massive shift

in the region from Buddhism to Islam,

the most prevailing theory revolves around

deadly volcanic eruptions.

Borobudur is located

in between two very active volcanoes.

Mount Merapi is one of them, and it's fairly famous.

It's about 15 miles from Borobudur.

And there were historically documented eruptions

that affected the area.

So, for the Javanese, this area is inherently sacred

and inhabited by deities and gods.

And the fact that you would have repeated volcanic eruptions

would have perhaps signaled at some point

that the gods were displeased with something

or that they wanted something to change.

But the story of Borobudur

becomes even more mysterious

when considering the geological record.

While it sounds obvious that volcanic eruptions

would be good cause for evacuation,

it appears that no major activity occurred

at the time the site was deserted

and left to be consumed by Mother Nature.

By the time we get to the 1700s,

the local Indonesians forgot it was even a structure.

All they knew was that there was a mountain out in the jungle

covered with a thousand statues.

People were afraid of it a little bit.

They didn't really understand or really know what it was.

The prince of Yogyakarta in the 1700s

had heard rumors about this place.

And he went there, and immediately after, he died.

And by then, clearly, it's seen

as a cursed site, an ominous site,

so the rumors of it being a place of danger and mystery

did continue to circulate up until the modern period.

Whether Borobudur was considered cursed

or merely left abandoned as a precaution,

today, millions of people visit this sacred site

to revel in its architectural grandeur

and imagine what was once at this

Mountain of a Thousand Statues.

Was the Borobudur Temple abandoned

because it was cursed by the gods?

Well, the only thing we know for certain

is that its construction was far ahead of its time.

Which was also the case with a mysterious Incan fortress

whose massive walls were built using stones

so perfectly placed that even a piece of paper

won't fit between them.

High in the Peruvian Andes,

overlooking the ancient city of Cusco,

lies one of the most baffling structures ever discovered.

It is called Sacsayhuamán.

And while time and warfare have transformed this site

into a shadow of its former glory,

it remains one of the most spectacular examples

of megalithic stonework in the world.

Sacsayhuamán is in the very heart

of the ancient Inca capital at Cusco.

And it's a gigantic, fortified structure.

It's got three layers of walls

that are really remarkable for their zigzaggy shape.

And it's the most patchwork kind of stonework

that you've ever seen.

And yet it's so precise.

It's something that archaeologists call

polygonal masonry,

and it's just a fancy word for saying

that all the rocks are of a different size and shape.

And these stones aren't just huge.

They're gargantuan.

Some of them weigh a hundred tons.

The Inca managed to fit them together

with these curves and lines so perfectly,

without any mortar, that you could not even

slide a blade of grass between them.

Our best guess as to when Sacsayhuamán was constructed

was under the Inca ruler Pachacuti,

who ruled beginning in 1438 till around 1471.

But we can't be sure because we don't have

any written records about it.

The Inca Empire used a system of recording

that was colored knots and strings,

and this is how they did their accounting.

And they even recorded history through this system.

But we don't actually have any records from the Inca

telling us what Sacsayhuamán was used for

or why it was built or who built it,

but probably most importantly, how did they build this thing?

While the techniques used to build Sacsayhuamán

remain one of history's great riddles,

we do know that in 1536,

the site became an Inca stronghold

during the Spanish conquest of Peru.

And in a great and bloody battle,

the Spanish slayed thousands and overtook the fortress,

which proved a key event in the fall of the Inca Empire.

The conquerors dismantled all but the largest stones

down to their foundation

and used them to rebuild Cusco in Spain's image.

Fortunately, famed chroniclers such as Garcilaso de la Vega

collected indigenous myths, legends and oral histories

related to this mighty stone masterpiece,

including the story of the site's original builders,

said to be here long before the Inca themselves.

Viracocha is the Inca creator god,

described in legend as being a pale-skinned figure

who rose out of the Pacific Ocean at some time

and gave rise to the first men, as they're called.

Some mythic race that some have said

are attributed with the building of Sacsayhuamán.

But other versions of the legend say that

Viracocha himself built Sacsayhuamán

and that the stones literally walked

into place on their own.

The story that I like most is that it's said

that a great serpent or dragons

created the stones

by petrifying the local Inca with its gaze

and that they then became the blocks that were then stacked

in this great puzzle of rocks, all interlocking.

Now, obviously, these are just legends, they're just stories,

but do they contain some kernel of truth within them?

While legendary tales may be metaphors

for lost civilizations or forgotten technology,

a more recent intriguing theory suggests

that the true secret of Sacsayhuamán

may be written on its walls in an ancient form of writing

encoded in the very stones themselves.

We have the remarkable construction of Sacsayhuamán.

We have to question why they created it like this.

Some people have suggested that all the different angles

and size and measurements at Sacsayhuamán

actually make up a code and this was part

of their sort of symbolic language.

It's almost like a message through time,

if we know how to read the signs.

And this isn't the only site in the area

that has this style of stonework.

We have places, very famous places.

Like Machu Picchu.

We have Ollantaytambo.

We have Qenko.

We have Tambomachay.

We have all these different sites

stretched all across the Sacred Valley.

And so, who knows?

When you start looking into things like this,

you realize that there's a whole other level of sophistication

that unless you study it you can't even see.

Could the written record of Sacsayhuamán

be encrypted within the walls themselves?

And if we can decode some hidden language,

might it be part of a larger message

that continues across other megalithic sites in Peru?

It's certainly an exciting proposition,

but until we learn how to decode these remarkable walls,

the mystery will remain as enigmatic

as the stones themselves.

In the southwestern heart of the country,

where fertile plains give way to rising mountain foothills,

there's an enormous stone figure that has towered

over the landscape for more than a millennium.

It is known as the Leshan Buddha.

The Leshan Buddha is this colossal structure

that sits literally almost in a throne

overseeing the confluence of three major rivers in the area.

It's carved out of the rock face of Mount Lingyun,

and it was built between roughly 700 and 800

of the Common Era, so over 1,200 years ago.

It's 233 feet in height,

which is actually the largest premodern statue ever recorded.

So it's quite an impressive sight.

And to cut this out of the rock face

requires just unimaginable

artistry and techniques.

The Leshan Buddha emerges out of this cliff

right at the junction of three

turbulent rivers.

These three rivers were an important waterway for trade.

But during the flooding season,

it would become so dangerous at that cliff.

And because of how many people lost their lives,

this is where this Buddha was chosen to be built.

As impressive as this massive sculpture is,

what is truly confounding

is that after the Leshan Buddha was completed,

it is said that the dangerous and turbulent waters

beneath its feet were almost miraculously tamed.

Remarkably, when the statue was completed,

there are records that show the rivers became calmer.

If you're a Buddhist,

then that tells you that the Leshan Buddha

would calm the waters of the river.

If you're not a Buddhist, then there's no real evidence

that Buddha came along and calmed the waters.

So, it seems that this construction,

maybe by design, maybe by happenstance,

affected at least the flow of the rivers

and this turbulent confluence and pacified them.

So, some people have interpreted this

as an action of the Buddha.

Others, historians, believe

that by strategically placing rock,

reworking the riverbanks and,

uh, realigning sediment

and rock at the bottom of the riverbeds,

that would have been intentional.

So there's a mystery there that remains to be, um, resolved.

Was it the benevolent power of the Buddha

that made these dangerous waters safe?

Or are engineering efforts responsible

for successfully altering the river's currents?

Perhaps both are true.

But as with so many structures of the ancient world,

their majesty and mystery continue

to amaze and confound us

as we seek to understand what appears to be impossible.

Megastructures from the ancient past

teach us a lot about what people in antiquity were able to do.

We think very highly of our own civilization,

and we tend to think that past civilizations

were very primitive in comparison.

And great structures show us

that not only could they do it,

we would actually struggle to do something like that today.

Whenever we see something

we don't understand, we become curious.

But in the absence of written records,

you have to rely on myth

and oral tradition to understand

who built these things, how and why.

And I think that mystery is going to remain a mystery

for a long period of time.

It's interesting to consider

what ancient cultures chose to construct out of stone,

a material difficult to work with

but one that defies the test of time.

Whether it's a 230-foot statue

said to calm violent waters,

massive walls that stretch for 13,000 miles,

or a temple complex carved from one solid rock,

there seems to be no end to the engineering feats

our ancestors could achieve.

And while we're able to marvel at these amazing structures,

we may simply have to accept that the secrets

of their construction and purpose

may forever remain unexplained.

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