Original subtitles

On a scale of one to ten,

if those anomalies are voids or passageways,

it's an absolute ten.

[narrator] A revolution in technology

is opening up a golden age of archaeological discovery.

[Jaskolski] This is it. This hole here drops off a good 60 feet deep.

Totally fatal to fall down.

[Guillermo "Memo" De Anda] Let's do it.

[narrator] And National Geographic has exclusive access

to document this ground-breaking journey.

[Jaskolski] Any time you do a dive with a bunch of new technology

and you come back with all the technology, that's a win, right?

[narrator] This team of explorers,

led by one of the world's foremost experts on the Maya,

are embarking on an unprecedented expedition.

[Chris Millbern] I'm definitely seeing stuff.

I'm pretty wildly excited right now.

[narrator] On a quest to stare deep underneath

the hallowed grounds of Chichen Itza

using lasers, drones,

and digital 3D modeling.

[Jaskolski] That's a big anomaly that I didn't expect to be there.

[narrator] All in an effort to unearth

one of the world's most epic mysteries

beneath one of the greatest civilizations.

The Buried Truth of the Maya.

Sixty-five million years ago...

an asteroid careened toward Earth

and smashed...

into Mexico's Yucatan Peninsula.

Its apocalyptic impact...

wiped out the dinosaurs

and killed 75 percent of all life on Earth.

Over time, thousands of sinkholes and underground caverns formed

through the cracks in the limestone.

Filled with water, these cenotes set the stage

for life to take hold once more.

Many millions of years later,

a highly advanced civilization formed around these water sources.

This life-sustaining resource fueled the rise

of the Maya,

the largest civilization in the Western Hemisphere at the time.

One of the most central and sacred sites in the entire Maya kingdom was called:

Chichen Itza.

Maya is a fascinating civilization.

They're in the middle of the jungle, they were so wise,

they did astronomical science,

and they do sacrifices or they do offerings into caves.

[narrator] Perhaps the ancient Maya understood this region's

cataclysmic past.

Because they also thought that to bring about water...

and life itself,

Chaac, the Maya god of rain, required offerings

such as jewels, bloodletting, and sometimes...

human sacrifice.

[Memo] Scholars have said that this is

the place to deposit the hearts of victims.

[narrator] Today, we're in a rare moment of archaeological discovery

in the world of the ancient Maya.

Recent scientific surveys suggest that the Maya could have built

secret underground tunnels and chambers

beneath Chichen Itza.

According to Maya folklore,

the most sacred cave, possibly full of generations worth of jewels,

gold, bones, and other lost treasures

sacrificed to the gods,

could lie beneath one of their holiest temples,

El Castillo.

But to this day,

this underground cave remains one of the greatest unsolved mysteries

at the heart of Chichen Itza.

Finding an entrance into this potential crypt under El Castillo...

would be one of the biggest discoveries of the 21st century

and could yield untold discoveries and archaeological treasures.

-This is a massive cavern. -Yeah, no that's huge.

-[Jaskolski] Memo! -[Memo] Hey, what's up!

[Jaskolski] Hey, man! How's it going?

-[Millbern] Good, buddy. -[Jaskolski] Good to see you.

[overlapping chatter]

[narrator] Uncovering it is bringing two teams of archaeologists

and technologists together.

[Millbern] Hey, we got something to show you.

-[Jaskolski] Yeah, yeah. -Check this out.

[Memo] All right.

[narrator] Guillermo de Anda, aka "Memo"...

is an INAH archaeologist, a National Geographic Explorer,

and one of the world's foremost experts on Maya archaeology

and their underground secrets.

I have been told for years in this area

that there is a huge cavern beneath El Castillo.

We know that caves have this big preservation factor.

It's going to be big news for the world,

it's going to be big news for Mayanists

if we find a way to get into the cave

beneath El Castillo.

[Jaskolski] This is from the droning, the LiDAR,

and the camera work around El Castillo.

[Memo] This is an amazing model, huh? The detail...

[Jaskolski] Yeah, it's really coming together, hey?

[narrator] Joining Memo is the pioneering technology company

Virtual Wonders.

Together, they're creating a high-tech 3D model of Chichen Itza

in the hopes of pinpointing an entrance

into the hidden well beneath the central pyramid.

[Jaskolski] My name is Corey Jaskolski.

At Virtual Wonders, I'm the Chief Technology Officer,

so responsible for getting all these crazy technologies to work

and come together and play well in the field.

Virtual Wonders goes around the world to cultural and natural places

and tries to 3D scan them

so that we can preserve and share these places

with the entire world.

Working in these ancient sites that are thousands of years old

with a ground-penetrating radar

or laser scanner that scans a million points per second,

you can only imagine what the people of those times

would have thought of these technologies.

They would have thought we brought down gifts from the gods

to help understand the world better

and, in a way, that's true.

Things that I get probably most excited about,

even far more than this data,

is El Castillo not being aligned

between Cenote Sagrado and Xtoloc.

[Memo] And we know the Maya didn't leave anything to chance.

What we believe is they are trying to put El Castillo on--

[Jaskolski] On top of something important.

[narrator] The city planners erected the pyramids at the proximate intersection

between four giant underground water wells called "cenotes"...

to the north, south, east, and west.

Curiously, the Maya built this pyramid 52 and a half feet off center

leaving it mysteriously unaligned,

which is unimaginable given the Maya's legendary mathematical

and architectural precision.

Some scientists believe that the Maya built this pyramid off-center

to tower above a pre-existing sacred cave,

forming a link to the spirits of the underworld.

Could this cave be filled with undiscovered treasures

and sacrificial offerings left for the gods?

[Jaskolski] I would have put this, uh, El Castillo

right between Xtoloc and Sagrado,

not, you know, not offset between the two.

The fact that El Castillo is not well aligned

with Cenote Sagrado and Xtoloc,

which as an engineer I look at that and I say to myself,

you know, if you asked me to build our biggest,

most important building for our culture,

I would have aligned it well between the cenotes.

It's off by about 16 meters,

which is a pretty big margin of error for the Maya.

[Memo] We have to look very, very hard on this

and work very hard on this because, Corey,

I want us there.

[narrator] The Ancient Maya's prowess in engineering,

mathematics, and astronomy

is legendary.

They invented the mathematical concept of zero,

and they designed their buildings with the heavens in mind.

This can be seen twice a year during the equinox,

when on the northern staircase of El Castillo,

the movement of shadows gives the impression of a serpent

slithering down into the underworld.

[Jaskolski] Not everyone would climb this, right?

It was only the priests and the rulers, right?

[Memo] Only them.

[narrator] Towering to impressive heights,

each of the pyramid's sides has 91 perilous steps.

Including all four sides,

the number of steps totals 364.

The final step into the sacred temple on top

totals 365,

the same number of days in the year.

[Memo] Wow!

[Jaskolski] This is something.

You really get a sense of its power,

which is why it existed,

to get closer to the gods and show the power of the civilization.

[Memo] We're closer to heaven.

We're on top of the big sacred mountain of the Maya.

Holtun right in front of us,

Sacred Cenote to the north,

Xtoloc to the south,

Xkanjuyum to the east.

[Jaskolski] To go up there with Memo and, uh,

you know, survey the land and look at what we're doing

is incredibly important.

So, I think there's definitely something under El Castillo.

We don't know what, and I think a lot more studies need to be done

in order to tell us for sure.

[narrator] To dig deeper into this mystery,

Memo and the Virtual Wonders team are looking to a recent study for clues

to find any entrance into the potential cave

under El Castillo.

With their new technology,

can they crack the code and find an entry point?

[Jaskolski] Memo, you'll remember this data,

this is, uh, from René Chávez.

[Memo] I remember this well. This is what started it all.

[Jaskolski] They put probes all over the ground around El Castillo,

and they measured the,

basically how well electricity flowed through the ground.

[narrator] Modern electrical systems generally employ metal wire

to conduct electricity,

but depending on the circumstances,

electricity can also conduct through soil.

[Jaskolski] What he found was these, these anomalies.

What he shows is an area of higher conductivity

they think may be a cenote under the El Castillo.

This is sorta what started it all. This was the...

There were a lot of sci-- There were a lot of media that were saying,

"They found a cenote for sure under El Castillo."

[Memo] Yes, I know, I know. This was a big thing.

[narrator] Various materials conduct electricity differently,

so what could be causing these areas of higher conductivity?

And could this be connected to an actual sub-surface world

beneath El Castillo?

[Memo] It's not confirmed data, but it makes sense

under the perspective of the oral tradition,

the legends, the myths around here that have always said

"There's something under Castillo."

[Jaskolski] Right.

If we can find the cenote, if there is a cenote or cave down there,

which I personally believe it is,

uh, we are going to find an amazing offering.

[narrator] Because of Chichen Itza's historic standing,

the team can't physically excavate the grounds.

However, by analyzing these data,

the teams develop a strategy to search for a long-lost entrance.

[Memo] The best chance is to go

-right to the center of El Castillo... -[Jaskolski] I agree.

...and see if we can get better results

and find a way to understand this, uh, thing better.

It needs a lot more exploration to figure out what it really is.

[Akasha Sutherland] Today's the GPR, Ground Penetrating Radar.

You're moving this lawn mower back and forth

and so while we're moving, then at the end we get this nice clear picture

of any voids or if there are any reflective spaces

that we don't know exactly what's below there.

[Jaskolski] So, we're actually, we're looking about 25 feet deep

through the ground here right now.

[Sutherland] Yeah.

[narrator] With the hopes of tracking down an entrance,

this device gives them basically x-ray vision below the earth

without physically altering it.

-[Sutherland] Slow? -[Jaskolski] Yeah, a little slower, yep.

There you go, there's the pace, yeah.

[Jaskolski] Akasha is our chief communications and outreach officer.

She's the reason that a lot of our field stuff runs smooth.

[Sutherland] I know how to use the LiDAR systems,

I am a strobe goddess.

So this takes thousands of images

to create a perfect 3D model of the structure.

It's all about hitting the ground just feeling comfortable with yourself

and once you have that established, then everything else is kind of cake.

[Jaskolski] I mean, her spirit is just unstoppable.

She is always happy, always smiling.

It doesn't matter what's happening. It doesn't matter

if, you know, we're injured and going to the ER.

She's got a big smile on her face

and is trying to lift everybody up around her.

-[Sutherland] How's it looking? -[Jaskolski] Looking good

[Sutherland] Yeah?

[Jaskolski] There's actually a little anomaly

at the beginning of those stairs.

[Sutherland] All right, I'm marking it right now.

-[device beeps] -[Jaskolski] Cool. Got the mark.

[Sutherland] Got it?

[narrator] The GPR immediately finds something.

Hints of a mysterious subterranean world rise up.

[Sutherland] We don't know exactly what's below there,

but we get this nice clear picture of voids

or reflective spaces.

[Jaskolski] All right!

And now we can go inside and catch the, uh, catch the inside bit.

[Sutherland] Let's go in!

[Jaskolski] Cool!

Try to bang that right up against the wall.

Just nice and slow. Nice and slow!

-[device beeps] -Cool.

-Whoa, I'm seeing stuff. Keep going. -[Sutherland gasps]

[narrator] This mysterious void,

found only a few feet away from El Castillo,

might connect to the hidden chamber below.

And if it does, could this void lead the team

to an undiscovered entrance

and possibly generations worth of ancient treasures

sacrificed to the Maya gods?

[narrator] Chichen Itza...

was a dominant capital of the Maya world.

Recent scientific evidence suggests the existence

of a mysterious chamber beneath the massive ruin of El Castillo.

[Jaskolski] I'm seeing stuff. Keep going.

[Sutherland gasps]

[narrator] And using high-tech tools,

the Virtual Wonders team, alongside Maya experts,

are trying to find an entrance into it.

[Jaskolski] The biggest anomaly was definitely

-on the entry over there. -[Sutherland] Okay.

[Jaskolski] We are indeed the first, uh,

to do the GPR directly under El Castillo.

That's a huge deal.

Nice and slow and steady if you can.

Yeah, we're seeing real good about 15 feet deep or so.

Past that, it gets a little noisy, but there's a lot we can do

to clean this up in the software too.

[Sutherland] Awesome.

[Jaskolski] Yeah, it seems like maybe three feet down or so

there's probably a layer of rock that might either be natural

or might be like the base that they built on.

-[Sutherland] Like, the substructure? -[Jaskolski] Right.

To be able to actually image what's beneath that, that floor is amazing,

Um, you know, on a scale of one to ten

if those anomalies are voids or passageways,

it's an absolute ten.

So we'll have to analyze the data and see what it looks like.

[Sutherland] Check it out.

[narrator] While Corey processes the data...

Memo brings another member of Virtual Wonders

into the restricted areas of El Castillo...

[Kenny Broad] When was the last time you were in here?

[Memo] Well, it was about a month ago, I believe.

[narrator] ...looking for any clues about the chamber below.

[Memo] It's magical just to be here

and thinking about how many thousands of stone

are on top of our heads, man.

So let's not think a lot about that.

[Kenny chuckles]

[Broad] My name is Kenny Broad. I'm the mission specialist.

[narrator] Kenny Broad is a National Geographic Explorer

and chief exploration officer of the Virtual Wonders team.

[Jaskolski] I would describe Kenny Broad as a, a mad scientist.

[narrator] As an expert caver,

he and Memo may be able to add crucial insight

on how to access the chamber below the pyramid.

[Memo] There's very few people that have the privilege to go in here.

-[Broad] I don't wanna wait. -[Memo] All right, let's go!

[Broad] Being involved in a new discovery,

it gives you this feeling that you're doing something larger

than just yourself.

[narrator] While there are no portals to the underworld on the ground floor,

they hike up to a sacred chamber

which holds some intriguing clues.

[Memo] And this is the...

[breathing heavily]

...amazing room.

-[Broad] Oh! -[Memo] So, here we are.

[Broad] Wow!

Oh my gosh, that's incredible

[Memo] Yeah, this is where the king used to sit.

[narrator] This is the jaguar throne.

[Broad] So the king used to sit here?

I mean, it really sticks out,

because it still has

-I assume the original paint? -[Memo] Yes.

[narrator] From this royal throne,

kings watched countless humans sacrificed

to the rain god Chaac

at this nearby altar.

Could their remains lie in the veiled crypt below?

[Broad] Those are the original insets of, is that jade?

[Memo] This is jade.

[narrator] To the Maya, jade was a royal resource,

used to communicate with the gods.

[Broad] But there's no local jade so--

[Memo] Exactly, yeah. They, they bring it all the way from Guatemala.

It was one very important item.

Only royalty had access to it.

This context is not only a royal context

where, where the king used to rest and sit,

it's also a funerary one.

There's a relationship with death here, and life.

[Broad, Memo] Resurrection.

-[Broad] The cycle. -[Memo] The jaguar is a cycle.

[narrator] The ornate Jaguar Throne sits in front of something

even more grim and ominous.

[Memo] This is an amazing wall for a number of reasons,

and, uh, what we see here is embedded, uh, bones.

They are long, long human bones

that are embedded on the wall.

There's one there.

Another one here.

There.

My assumption as an bio-archaeologist, I believe these are leg bones.

-[Broad] Looks like it would be a femur... -[Memo] Exactly. Or tibias.

If you ask me, I would say yeah, that might represent

bones of ancestors.

[Broad] Right.

[Memo] Or people very powerful.

[Broad] What's your sense of what could be behind this wall?

Well, I do really believe that there is,

uh, something intentionally deposited there.

Given the sacredness of the site,

the importance of the place within Chichen Itza,

I believe it could be a burial back there.

[Broad] I mean, it makes logical sense.

It makes sense, yes.

Yeah, if somebody is buried here,

it was for sure a very important person, a king.

[narrator] Could the chamber behind this wall of bones

have once provided a gateway to the cave below?

[Broad] I can feel the wind coming through here.

-It's like you've found a lead. -[Memo] Oh yeah, yeah. You feel that?

-You feel that? -[Broad] Yeah.

[Memo] That could be indicating a system down there.

[Broad] No, and right, when we explore caves,

we look for that kind of breeze.

That's a, that's a sign.

[Memo] When we feel that breeze, it's, "Let's go."

-[Broad] Yeah. -[Memo] Yeah, so...

[Broad] Some more evidence that there's something beneath.

[Memo] And I think this means that

the cenote that we're looking for might be down there.

Or maybe an entrance.

-[Memo] And you can see some, some voids. -[Broad] Right. Right.

[narrator] Because they can't physically alter anything inside El Castillo,

Kenny and Memo carry on

looking for other ways in, to no avail.

But back at the Virtual Wonder's headquarters,

Corey and Akasha have processed their GPR findings

and discover something promising.

So we did this north face first and, uh, went along this way,

right along the fence line, about, uh, about a half a meter from the fence line

and then this way and this way.

But what we're seeing here,

um, these areas of black, white, black like this

are very strong radar returns.

I don't think they indicate a void to me,

but I think they indicate rock.

There's nothing that interesting on the north side to me.

We then started over here

and dragged the south side of the GPR right on the corner here.

Again, there seems like there's a rock base,

but what's really interesting to me is this return.

So this is in the, uh, south east corner of El Castillo,

This is between three and four meters deep over here.

-Oh, wow, that's deep enough. -[Jaskolski] And there is, uh,

there is what looks like a really strong return.

[Memo] And it looks like a very irregular cavity, right?

It looks, uh, I mean, from a single GPR radar-gram like that,

yeah, I would say that looks like a cavity, yeah.

So like a natural cavity, I mean?

[Jaskolski] It's hard to say. It's hard to say if it's natural or man-made.

All you can really say is it's a really strong return

that looks like a void.

How far actually it's from, from the corner?

It's almost exactly on the corner.

Okay, that's very, very interesting.

-[Jaskolski] Yeah. -Wow.

[Jaskolski] What I now want to show you, Cash and I took the GPR

in this, uh, excavated archaeology part

underneath here, this doorway and we dragged it back,

and then the hallway turns and goes into El Castillo

towards that rock fall.

Towards the center of El Castillo?

[Jaskolski] Right. This right here,

um, is the brightest radar reflection I've seen

anywhere in Chichen Itza.

-I've been dragging this radar around. -[Memo] It looks amazing.

[Jaskolski] This is to me a pretty clear void,

um, at, look at that, three to four meters deep.

Corey, I think this is amazing,

but what I think what amazes me more is

that both anomalies are the same depth.

-Yup. -So it might be a tunnel,

and that's very promising.

[narrator] Could this potential tunnel be the gateway

to the proposed cenote below?

If so, where is its entrance?

[Jaskolski] The thing with GPR that I always think about is,

if you see something and you don't see anything like that anywhere else,

then you're like, okay, one weird anomaly,

but the whole thing is with GPR when you start building up a story,

when you start saying, whoa, we're seeing weird stuff

at three and a half to four meters here...

Might have comparison.

[Jaskolski] You may be, you know, I think it builds more meaning to me.

That's a, that's a big anomaly that I didn't expect to be there.

None of the rest of the area looks like that.

The other side that goes up the substructure

doesn't have any returns that look like this.

This is a, this is a big neon sign

-saying there's something interesting. -[Memo] Yes!

That might be it.

[narrator] This possible tunnel may lead in the direction

of another Chichen Itza landmark:

El Osario.

El Osario is also known as the "Tomb of the High Priest."

Another temple on the grounds of Chichen Itza.

Archaeologists have traditionally thought that El Osario was built

in 980 AD

and modeled after its bigger sister: El Castillo.

But there's an even more stunning parallel.

El Osario kind of replicates what we see in El Castillo.

[Jaskolski] Yeah, it looks very much similar, yeah.

[Memo] It's a radial pyramid, four, uh, axis stairways,

snake, snake heads at the end,

so the similarities are amazing

why not thinking there is a cavern also in El Castillo.

Guess what, El Osario was built

right on top of a natural cavern.

We think that this cavern might have tunnels or passageways

to get into this other tunnel.

That makes sense

because they are very close,

so it sounds like the logical place to find a passageway

to El Castillo.

[narrator] The question is: do these underground passageways

connect to the chamber beneath El Castillo?

They clearly built the Osario to be over that important cave.

[narrator] Because of the danger, climbing El Osario

is restricted to the general public.

[Jaskolski] Just a set of Mayan stairs, and they're super-steep.

They're probably, like, a 45-degree angle,

like the stairs outside of El Castillo.

[Millbern] All right! So, we'll connect this up?

[indistinct chatter]

-[Memo] We're looking for tunnels here. -[Jaskolski] Yes.

I want you guys to look for possible areas or gaps

and see if there's a passageway behind.

[Jaskolski] Totally. Yep.

[narrator] To find any tunnels,

the team must use their high-tech tools

in a difficult to reach spot.

[Memo] Very few people have been here,

and, uh, nobody has been here with this technology.

-Has used technology, right? -Yeah.

I guess they had, uh,

1800s technology last time they...

It still counts, it still counts.

My name is Chris Millbern,

and I'm the director of field operations.

Anything that has to do with tech or gear is under my purview

or at the very least is me messing around and running around

to make sure that it works.

-Robot, cable, tablet. -Yeah.

-Only three giant things, it will be fine. -[Jaskolski] Yeah.

I'm definitely the one sweating the most

if nobody's noticed.

Let's go! Let's do it!

-[Jaskolski] Right! -[Memo] Okay.

[narrator] To get underneath El Osario,

they must risk life and limb.

[Memo speaking Spanish]

[Jaskolski] Memo's about to come down. Are you ready?

That hole is about a 60 foot drop straight down.

Going down into this little tiny cave.

[Jaskolski] Geez!

[Millbern] Corey's on the way down!

[Jaskolski] Right, coming down.

Not a lotta room, eh?

[Memo] Not a lot of room, man.

-[Jaskolski] What's the drop? -[Memo] Sixty feet.

[Jaskolski] Sixty feet. But this is it.

We're... we're crammed in here.

[Memo] How dangerous this place is?

-[Jaskolski] Yeah, man. -Uh, any rock...

-[Jaskolski] Yeah, you're dead. -You're dead.

Woo!

[Jaskolski] It's this tiny, tiny little room.

I mean, you feel like you're in the womb.

You're just crushed in there with Guillermo.

This must have been such an important place for the Maya

to build this massive monument on top of it.

[narrator] To find any undiscovered passageways

and where they might lead,

the team breaks out one of its most versatile devices.

[Millbern] All right, Corey, borescope on its way!

[narrator] The borescope has a small camera

that can snake around nooks and crannies.

[Jaskolski] Okay.

So I'm going to feed out the borescope cable.

-[Memo] Okay. -[Jaskolski] And Guillermo,

so we'll have to straighten this out so the borescope can articulate

so be careful.

Uh... all right, Memo, start going.

[Memo] Okay.

[Jaskolski] Go a little bit more in.

Yeah, we got something interesting. Here, look at this. What is this?

[Memo] I think this is the original entrance to this cave.

-[Jaskolski] Oh, right there. Right. -Yes.

-[Jaskolski] Yeah. Oh my God! -And, uh...

[narrator] But there's something even more intriguing

about this underground entrance.

The passageway has been mysteriously blocked

by something man-made.

[Jaskolski] Do you think they're cave-in, or do you think

they were, uh, blocked by the Maya?

-[Memo] No, no, I think it was the Maya. -Right.

-[Memo] The ancient Maya sealed it. -Yeah, yeah.

-Okay. -[Memo] It was, like, completely blocked.

[narrator] Memo believes the ancient Maya did this

because of where the passage points.

[Jaskolski] I feel like the blocked passage

is in the direction of El Castillo.

-Wow. -[Memo] Yeah.

[narrator] But why would the Maya have blocked off

an underground passageway between El Osario

and the chamber below El Castillo?

The team carries on its investigation

and stumbles upon a relevant clue.

[Jaskolski] I'm seeing something on the walls.

See the white?

Stop there for a second.

What's that?

[Memo] Right there we see a piece of pottery.

-[Jaskolski] Oh, that's pottery? -Yeah, oh yeah.

[Jaskolski] Wow, wow, hold on there for a second

-[Memo] You see all the ceramic there? -Where?

[Jaskolski] Is that... Oh yeah!

[narrator] The Maya ritually broke ceramic pottery

as sacrificial offerings

alongside the people they buried

in order to free their spirit.

But the place the team has found these ceramic shards

is even more mystifying.

[Jaskolski] The ceramic is on a little shelf up there, right?

-Is that what you're looking at? -[Memo] No, it's not a shelf.

It's on the ceiling--

-[Jaskolski] The ceramic's on the ceiling? -[Yeah.

[Jaskolski] You find pottery all over the floor of the caves all the time,

but shards of pottery, you know, hanging down like... [chuckles]

...you know, like they could fall on you like knives from the ceiling,

and, you know, that's, that's weird.

And that's the ceiling we're pointed towards, right, you said?

-[Memo] Yes, exactly. -[Jaskolski] That's crazy.

[narrator] What would have prompted the Maya to affix broken pottery

to the ceiling of this sacred underground chamber?

[Jaskolski] Is it ritually sacrificed pottery?

[Memo] Yeah, it is ritually sacrificed.

They, uh, used fire as part of the, of the ritual.

-It's charcoal, mud, and ceramics. -[Jaskolski] Wow!

[Memo] And then they mix it all together.

[Jaskolski] You think they filled this in?

-[Memo] Yeah. -So that's the floor, really?

We're looking at maybe the floor of what they filled in?

But it's our ceiling.

Wow!

They mixed pottery, charcoal, and dirt

and filled that in from the outside to close off a passageway

so that the Osario shaft was the only passage into this sacred cave.

You know, that's, that's weird.

[narrator] But why did the Maya intentionally block

this underground tunnel?

Before they can investigate any further...

[thunder rumbling]

[Millbern] Ooh boy, that's gonna be a big one.

Oh [bleep]!

Lightning is probably my least favorite.

[lightning cracks]

[narrator] An unexpected storm threatens not just the investigation,

but the lives of the men below.

[Millbern] A storm of that size is not something I like to be around,

next to a metal structure, with my friends in a wet hole right down below.

[Jaskolski] We can't tell it's raining at all,

but we hear Chris from the top yelling down,

"Guys, you better hurry up!

The lightning's coming in." And we're like, "Oh no!"

Let's go!

[lightning cracks]

[narrator] At Chichen Itza's pyramid, El Osario...

archaeologist Guillermo de Anda

and cutting-edge technologists Virtual Wonders

are trying to unearth an access point

to the tunnel that could connect to the chamber below El Castillo.

-[lightning cracks] -[Millbern] Ooh boy!

[Jaskolski] Let's go!

[narrator] But their search comes to a grinding halt when lightning strikes.

[Millbern] So lightning's coming in and so is the rain,

so we're trying to get these guys out of the hole

as soon as possible.

This is a little scary.

[narrator] Trapped in this tomb 60 feet below,

they must evacuate before it's too late.

[Jaskolski] All right. Gracias.

-[Millbern] There you go! Nice. -[Jaskolski] Gracias.

People have died being hit by lightning.

We've got this big metal frame around it that's being used to lower people.

Whoo!

That was... that was crazy.

The lightning's just ripping down all around.

Let's get outta here before we're hit by lightning!

[man] Yes.

[Jaskolski] Yeah, yeah. Chaac is, uh, Chaac is with us.

[narrator] Safely out of harm's way,

the whole team reviews what they found beneath El Osario

to try and work out why the Maya blocked off

this underground passageway.

[Jaskolski] Basically, we put the borescope in everywhere it would fit.

[narrator] To help resolve this mystery,

Maya archaeologist Dr. Jim Brady joins the team.

[Dr. James Brady] That's really terrific!

-[Jaskolski] The pottery's right here. -[Millbern] Oh, is it that structure?

[Jaskolski] There's all the shards there.

[narrator] Dr. Brady is one of the few archaeologists

to have really explored the mysteries of El Osario.

His expertise could yield crucial insight

into this enigmatic blocked passageway.

[Jaskolski] Which is crazy, right?

I mean, having the pottery shards on the ceiling was a surprise to me.

I didn't know that was down there.

-[Memo] There. -[Jaskolski] And here's, here's charcoal,

and is that, that's charcoal, and that is charcoal, too?

[Dr. Brady] Yes. Those are bits of charcoal.

[Jaskolski] Okay.

[Dr. Brady] We sampled that charcoal

and have gotten a radiocarbon dates back

that come out about, oh, 725, 728 AD.

[Jaskolski] 725? Wow.

[narrator] Traditionally, most scholars believe

El Osario was built in 980 AD.

But recent research is turning this notion on its head.

[Dr. Brady] The Osario was built much earlier than people think.

This is about two and a half centuries earlier than--

-[Jaskolski] Really? Wow. -[Dr. Brady] Yeah.

[Jaskolski] Yeah, yeah, yeah.

[Millbern] How much earlier does that place it

in comparison to other buildings?

[Jaskolski] Like, what's El Castillo do you think?

The Castillo would be later

and so this is gonna change everything--

Yeah, yeah, yeah, yeah.

[Dr. Brady] This is gonna change everything because rather than

the Osario being a model of the Castillo

it might be the other way around.

[Jaskolski] Yeah. Totally. Wow.

[narrator] The carbon dating of the charcoal is changing history

and proves El Osario was likely built before...

El Castillo.

And for the team, the ritual use of charcoal beneath El Osario

also provides a significant piece of the puzzle.

[Memo] The pot shards and the charcoal,

you know, that might be indicating

some kind of a ritual.

[Broad] Is this sort of the same idea that how they

packed everything off, closed something off?

-[Memo] Like termination ritual, you mean? -[Broad] Exactly.

What do you think, Dr. Brady?

It looks like it was terminated.

[narrator] A termination ritual is the act of killing a building's spiritual force.

This exorcism typically happened when the Maya abandoned their temples.

The termination ritual not only closed off a building to the living,

it also stopped the temple from being visited by the dead.

-[Sutherland] That's crazy! - [Jaskolski] Right?

[narrator] El Osario may have once had an entranceway

to this now blocked underground tunnel,

leading to the subterranean chamber beneath El Castillo,

and even been part of a sprawling subterranean world.

But because this possible passage is now blocked,

the team must regroup.

[Memo] That, that's very interesting,

you know, we've been desperately trying to get,

to find an entrance to this cavern or cenote

if there is one right under El Castillo.

[narrator] Memo, who knows the Chichen Itza underground

better than anyone on Earth,

knows of one possible opening to the Maya underworld

that could provide an underground gateway to El Castillo.

The only way to access it is by using advanced technology

and facing extreme dangers.

[Memo] Watch out for snakes, please.

Yeah, the cenote is right there.

[narrator] The cenotes, ceremonial sacred sites of the Maya,

could provide concealed entranceways

to a sprawling underground network of long-lost passages.

But flooded with water,

they're notoriously difficult to explore, even deadly.

[Memo] It's going to become a little bit more slippery so careful with that.

We're gonna use a rope just to help ourselves going down there.

[narrator] Despite this, Memo and the Virtual Wonders team are trekking

to one of the four cenotes that surround the central pyramid of El Castillo.

The treacherous and seldom-explored underground cavern called...

Holtun.

[Memo] This is the amazing thing about technology

that we can see things that the eye can't.

I'm so glad that today we have this little robot

because, uh, there is a huge tunnel

that turns a little bit to the north which El Castillo is,

so that might be a very good chance

to maybe connect to the cenote under it.

Every time I go down there, I find something new.

Let's go diving.

[narrator] For the team, searching these under-explored chambers

might be their best chance at making a groundbreaking discovery

that could unlock one of the ancient Maya's greatest secrets.

And if so, what riches could they find?

[narrator] In their quest to reveal a secret underground passageway

and resolve the mystery at the heart of Chichen Itza,

Virtual Wonders and Maya archaeologist Guillermo de Anda

are making their way to one of the four major cenotes

that surround Chichen Itza's main pyramid.

Deploying the most advanced exploration tools available,

they plan to investigate the westernmost cenote...

called Holtun.

[Memo] This is the entrance.

We can go to the south side wall.

[narrator] Searching for an underground passageway

that could lead to undiscovered treasures beneath El Castillo.

[Memo] Cenotes have this mystery.

There is passageways that goes who knows where.

[indistinct chatter]

[Memo] Okay.

On rope!

[speaking Spanish]

[narrator] It's a potentially fatal 72-foot drop,

perilous not just for the divers, but also for the pricey gear.

-[Jaskolski] You good, Chris? -[Millbern] Yeah.

-[Jaskolski] All right. -[Millbern] Okay.

[narrator] Corey and Memo will scuba dive to look for any concealed passageways.

[Millbern] Okay, we're in business.

[narrator] While field specialist Chris Millbern pilots the ROV

from a raft inside the cenote.

This small robot submarine fits places that humans

with their bulky scuba gear are just too big to go.

[man] You're going down with a bag?

[Millbern] Si.

It is exactly as insane as you would expect.

This is not a carved-out cave that's really comfortable.

It's not a place that a lot of people have been.

Okay!

It's some place that you have to really know your stuff to get down into

and you have to take some risks to make sure that your able to see it.

-[Jaskolski] Is that you? -[Millbern] Yep, that's me.

[Jaskolski] All right, go.

Cool. Props are turning.

There you go.

-You have video? -[Millbern] Yep.

[Jaskolski] All right!

Are you on the slowest mode possible?

[Millbern] I'm on the slowest mode possible.

Stabilization's off, 'cause I want it to be off.

[Jaskolski] Okay.

-[Millbern] Have a good dive now. -[Jaskolski] Yeah. Thanks, buddy!

We'll see you soon.

[rebreather hissing]

[Millbern] Go find something.

[Jaskolski] Generally, I'm against using technology like ROVs in cenotes,

and the reason is 'cause they have little propellers that spin

and that kicks up sediment and silt in a lot of places,

and that sediment or silt could contain little bones

or bits of Mayan incense, charcoal, offerings like that.

[Millbern] I apologize for being silent.

I'm just, I'm so intently focused.

[Jaskolski] But being able to have a talented ROV pilot

maneuver it through to see where that passage goes,

that's critical because this place has become incredibly sacred to me.

[narrator] In this underground lair of the Maya gods,

the team finds extensive evidence that Holtun

was a primary repository for human sacrifice.

[Millbern] Oh, oh, oh.

Come on. Come on, baby!

Keep moving.

My mom said video games weren't a career.

I'm definitely seeing stuff.

Wow! This is beautiful.

We found a new cave. I am...

I am pretty wildly excited right now.

I think this keeps continuing.

[narrator] At the iconic Chichen Itza,

Virtual Wonders and Memo de Anda

have found an undiscovered, underwater passageway...

[Millbern] I'm definitely seeing stuff.

[narrator]...that could lead to a hidden chamber below El Castillo.

[Millbern] Wow! This is beautiful.

We found a new cave. I am...

I am pretty wildly excited right now.

This is definitely its own cave passage worthy of exploration.

There's the entrance.

I'm very afraid of getting stuck,

but, you know, that's how cave exploration goes.

[Jaskolski] Back in Mayan times, that passage would have been dry,

so it would have been pretty easy to go through on your belly

and crawl through the, the cave and to go make offerings.

[Millbern] Okay, let's turn.

We're definitely in a, in a large passage that, uh...

could have artifacts.

I'm checking all the shelves that I can see

to see if there's anything that looks man-made.

This is spectacular!

What I'm trying to do is fight buoyancy essentially

and go a little bit farther.

I'm trying to be very careful

so that if there is anything in here that I don't disturb it.

The difference between rock and artifact

is, is gonna be something that we might have to look at later.

So I'm checking all of the shelves that I can see

to see if there's anything man-made.

I actually see fish way deep there in the cave which is amazing.

Uh, I'm really hoping not to disturb anything,

so I have to be really careful, but this is spectacular.

I, I honestly can't believe it.

I had no idea that this was gonna be on the other side.

[narrator] The question is: where does it lead?

Could it lead all the way to a crypt beneath El Castillo?

[Millbern] It definitely goes.

[Jaskolski] In cave terminology, we know that that passage "goes,"

meaning that it continues on past what we can see.

How big would you, did you think the passage was?

[Millbern] Uh, it could be 10 to even 30 feet up.

I mean, it was, it was tall.

It's really hard, it's hard to get scale on this video

so before I, you know, make a grand claim...

Uh, but it, it was big enough to fit a person definitely,

and it looked like it went up pretty tall.

[Jaskolski] Wow!

We'll, we'll have to review the video though

'cause, again, I can't get scale out of this video.

[Jaskolski] That's awesome!

These passageways never go straight.

-[Jaskolski] Right. -I mean, very...

[Jaskolski] This one definitely doesn't.

[Millbern] This one didn't go straight. This one went up, left, right and down...

It could have gone in any direction.

-Absolutely. -[Memo] Okay.

There was a lot more to it than what we saw.

[Memo] We found a passageway.

[Jaskolski] Really successful dive.

Gracias. All right.

Any time you do a dive with a bunch of new technology

and you come back with all the technology

and everything looks like it worked,

-it's a win right? -[Memo laughing] Oh, yeah.

We gotta check it out on video, man. I'm excited.

[Memo laughs] Yeah. I feel amazed

and with a lot of hope that

this can take us towards Chichen, but Chris said it's...

-[Jaskolski] It bends. -[Millbern] Multiple directions.

I think we had options so who knows.

It certainly is really lucky that we had this tool with us

because there was no other way we were seeing it today.

[narrator] Back at tech headquarters,

the team scrubs through the ROV's footage together,

hoping to gain more insight into this newly discovered passageway

deep inside Holtun.

[Millbern] All right, so wait until this just goes over.

I want to show you something really cool.

So this was the constriction that was hardest for me to get through.

[Memo] Yeah, that, that was a hard one.

No one's ever been back there, right, Memo?

This is unexplored caves?

[Memo] No, no, this is completely unexplored.

[Millbern] So, obviously, it extends up this way,

and there's actually a little bit of passages that come back

around on the back.

And then, when it drops down here...

you'll see openings all across the bottom.

I mean, it's, it's huge compared to the crevice

-that it actually started at, you know. -[Memo] Yes. Yes.

[Jaskolski] Right, right, yeah.

[Millbern] Look down here.

You've got a passage that comes here, and it also goes in this direction.

[Jaskolski] Wow!

[narrator] Though they can't tell if the passageway ultimately extends

to the potential cenote below El Castillo,

they do collect important evidence.

[Millbern] So zoom it back just a little bit.

[Jaskolski] Zooming it back.

[Millbern] Now, here's where I want you to check out.

[Memo] Oh, that looks like bones.

[narrator] These bones could be the remains of offerings

to the gods.

But that's not all the team discovers.

[Jaskolski] Oh [bleep]! Hey! Hey, hey, hey, Memo!

What is that? What is that green bit right there?

-[Memo] Oh yeah? -[Sutherland] Oh my god.

[Memo] Looks like a jade bead.

[Jaskolski] That was jade.

[narrator] Jade.

[Memo] Wow! [laughs]

-[Jaskolski] Yeah, totally. -[overlapping chatter]

[narrator] In the ancient world of the Maya,

jade was a royal resource and a precious commodity,

used to communicate with the gods.

[Jaskolski] That's an offering, yeah.

[Millbern] Good eye, Corey!

[Memo] Yes!

[narrator] Only the elite could make a sacrificial offering of jade.

Inside this cenote that had mysteriously run catastrophically low

through a prolonged drought,

the rulers may have believed that the end of the world was near.

I would suspect when there's the worst droughts,

there are probably the most sacrifices.

[narrator] Finding jade here in this newly discovered passage

could be a momentous breakthrough.

In a desperate plea to the gods,

the Maya elite could have used this place

to offer their greatest treasures,

all for the sake of rain.

-There's another one. -Yeah.

This one. Look, this, this.

Wow!

[narrator] These offerings may have been a last-ditch appeal to the gods

to save the city of Chichen Itza

from apocalyptic doom.

Gradually, by the 11th century AD,

this Maya capital collapsed,

largely due to an epic drought that lasted over 15 years

causing the nearby cenotes that sustained the city

to run dry.

The effects of this drought gradually undermined the city

of Chichen Itza,

and it was eventually abandoned.

But this newly discovered passageway,

riddled with evidence of sacrifice could someday lead

to even more offerings and treasures

and into the mysterious cave below El Castillo.