Unearthed

Chichen Itza,

a spectacular ancient Maya city

shrouded in mystery and myths.

It's the greatest ancient city in the world.

It's a jungle Metropolis

with a hidden underworld and dark secrets.

What happened to this lost civilization?

The big question that drives us is why people were here.

How and why was this vast city built?

And did the people living here practice human sacrifice?

The only way to solve these mysteries

is to go deep into the heart of the Mayan city.

Exploring its structures stone by stone

will help us unearth the astonishing secrets

at the heart of this ancient wonder.

captions paid for by discovery communications

Chichen Itza, Mexico.

A thousand years ago, this was a powerful working city...

Home to 30,000 people... the ancient Maya...

a civilization known for their remarkable skill

in astronomy, mathematics, and architecture.

And for their blood-curdling religious rites.

Archeologist memo de anda has spent much of his lifetime

trying to make sense of this mysterious jungle city

and it's awe-inspiring buildings.

We're just scratching the surface.

That's literally what we're doing.

I'm sure this building is still hiding

many, many secrets inside.

The ruins of more than 30 ancient structures

and temples lie hidden here amongst the trees,

including this immense pyramid.

The castillo, or temple of kukulkan,

one of the new seven wonders of the world.

Built from tens of thousands of limestone blocks,

it towers 100 feet high... as tall as a 10-story building.

At its peak, a sacred temple

dedicated to the serpent god kukulkan.

On each side, steep steps that reflect he Maya calendar.

And at the base, serpent heads linked to the equinox.

This 60,000-ton structure is a marvel of ancient engineering.

This is one of the most wonderful buildings

from the ancient world.

It's a demonstration of power,

a demonstration of spirituality,

a demonstration of science.

It's an important building.

Why did the ancient Maya

build this spectacular city in the jungle?

And how did they source the many thousands of tons

of stone needed to build huge temples and pyramids like this?

One-third of a mile from the main pyramid,

memo is searching for clues.

It seems this is no ordinary jungle.

The Maya didn't have to really go far away

to find the material to build their big cities.

Limestone... it's everywhere.

The material is beneath their feet...

all this material is right there.

The limestone lay within very easy reach.

The soil is very, very thin.

It's not even two centimeters of soil

that's laying over the huge limestone bedrock.

It's limestone all around us.

It's actually the whole peninsula.

It's a big limestone platform.

Limestone was the crucial ingredient

that allowed the Maya to construct Chichen Itza's

great buildings.

Workers mined it in this quarry

just 500 yards from the castillo pyramid.

Memo uncovers some extraordinary evidence to prove it.

Right here, we can see a pre-form.

It's a huge piece of rock... of limestone...

that they started working.

'Cause, see, this is perfectly round,

and we can see on one side the start of the formation

of a mouth of a snake.

But somehow, they leave it here.

Maybe because it got broken.

A remarkable clue carved by a Maya craftsman

a thousand years ago.

And it shows us by being here

is that they obtained the material,

and they work it right here.

They take it when it was finished up to the city.

So that's pretty amazing.

The local geology provided Chichen Itza's builders

with an endless supply of limestone.

But there's a further mystery.

The ancient Maya had no access to metal tools.

How did they get this stone out of the ground?

It is interesting,

and it's amazing at the same time.

How can they build these fantastic cities

only with stone tools?

The resourceful Maya

came up with an ingenious solution.

They used shards of razor-sharp stones like chert,

sometimes attaching them to wooden sticks.

They gouged deep channels into the ground,

carving a checkerboard pattern into the limestone rocks.

The workers dug down until they reached

a natural break in the limestone bedrock.

This way, the checkerboard blocks

would crack away from the ground.

Then they used wooden levers to pry the blocks out.

How much effort did it take to remove heavy limestone blocks

without modern machinery?

To find out, memo is heading to a stone masons yard in Merida,

about 70 miles from Chichen Itza.

The stone masons attempt an experiment.

They use wooden levers to try to extract

a two-ton limestone block,

just as the ancient Maya would have done.

All the stones they put there to make a lever.

I think we put a little bit too many.

So we need space for the big lever.

These guys are extraordinarily skillful and strong.

I mean, they're great.

So far, so good.

Shifting the limestone the old fashioned way

clearly required both technique and plenty of manpower.

Today, that I have the opportunity

to move this relatively small stone

and it was so hard.

And there were a lot of people,

I realized how hard it was.

And I'm getting more and more and more respect for the Maya,

for what they do.

It's amazing.

Wow, that was great.

These guys are great.

Wow.

Moving one stone was back-breaking work.

Yet this pyramid is made of tens of thousands

of limestone blocks.

How did the ancient Maya build it?

The secret to constructing this amazing temple

lies hidden inside

because this pyramid isn't quite what it seems.

Concealed beneath the smooth facade is a layer of rubble.

Under that, an older pyramid,

roughly half the castillo's size.

Its staircase leads to a sacred temple with two chambers.

At their heart, a throne in the shape of a Jaguar

with Jade stone eyes and white flint teeth

and a mysterious reclining statue known as a chac mool.

Building on top of this existing temple

was an ingenious way to build big

as a new era in the life of the city dawned.

The ancient Maya, they did not destroy a building

to build another one.

They just go ahead and built on top of the old building.

And built something majestic like this.

But why did the ancient Maya

build a great city here in the middle of dense jungle?

In the vast landscape of the Yucatan,

why did the ancient Maya choose this location

for their city?

To find out, geophysicist Rene Chavez

is 75 miles west of Chichen Itza city.

Using a new technique to see beneath ancient Maya pyramids,

he believes the answer may lie underground.

This is one of dozens of ancient pyramids

hidden in the Mexican jungle.

It may look very different from the famous castillo,

but it's what many Maya pyramids look like

before archeologists restore them.

We have to deploy the electrodes on top of the pyramid...

Rene's team lays a web of electrodes,

which they will use to send

an electrical current through the ground.

The team will measure how easily the current travels.

Their readings will reveal if any structures

or strange natural formations lie beneath the rocks and soil.

It takes time to process the data from today's survey.

Rene can only hope it provides results

as spectacular as his recent findings

from a similar investigation

at Chichen Itza's great castillo pyramid.

In this model, each color represents

a different geological material.

Rene's results reveal something extraordinary.

Hidden directly beneath the castillo pyramid,

below a five-yard-thick layer of limestone

sits a giant underground cave full of water...

a formation known as a cenote.

The cave contains as much water as six olympic swimming pools.

It extends over 65 feet underground.

Building a pyramid right on top of a cave

full of water might seem surprising,

but its existence here has dramatic implications

for our understanding of this iconic temple.

Without digging, there's no way to access the cenote

hidden under the castillo.

So archeologists memo de anda

is visiting another nearby cenote

to investigate what may lie beneath the pyramid.

Isn't this wonderful?