Original subtitles

Corey jaskolski: On a scale from 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.

Corey: 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 groundbreaking journey.

Corey: Anytime 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 chichén itzá...

Using lasers, drones, and digital 3d modeling.

Corey: 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.

65 million years ago,

An asteroid careened toward earth,

And smashed into mexico's yucatán peninsula.

Its apocalyptic impact wiped out the dinosaurs

And killed 75% 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...

Chichén itzá.

Memo: 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 chichén itzá.

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 chichén itzá.

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.

Corey: This is a massive cavern.

Chris: Yeah, no, that's huge.

Corey: Memo! Memo: Hey, what's up?

Chris: Hey, man!

Corey: How's it going? Good, buddy. Good to see you.

Chris: Long time no see, man!

Narrator: Uncovering it is bringing two teams

Of archaeologists and technologists together.

Chris: Hey, we got something to show you.

Corey: Yeah, yeah. Check this out.

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.

Memo: 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.

Corey: This is from the droning, the lidar and the camera work

Around el castillo.

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

Corey: 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 chichén itzá, in the hopes of pinpointing an entrance

Into the hidden well beneath the central pyramid.

Corey: 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've 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...

Corey: 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?

Corey: I would have put this,

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.

Corey: Not everyone would climb this, right?

It was only the priests would have, or the rulers, right?

Memo: Yes, yes. 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!

Corey: 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.

Corey: To go up there with memo

And to, 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?

Corey: Memo, you'll remember this data,

This is from rene chavez.

Memo: I remember this well, this is what started it all.

Corey: 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.

Corey: What he found was these, these anomalies.

What he shows is an area of higher conductivity,

They think maybe a cenote under el castillo.

This is what sort of started it, all this was the...

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 subsurface 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.

Corey: Right.

Memo: If we can find the cenote,

If there is a cenote or a cave down there,

Which I personally believe it is,

We are going to find an amazing offering.

Narrator: Because of chichén itzá'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.

Corey: I agree.

Memo: And see if we can get better results

And find a way to understand this thing better.

Corey: 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 voids,

Or if there are any reflective spaces

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

Corey: So, we're actually, we're looking about 25 feet deep

Through the ground here right now.

Akasha: 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.

Akasha: Slow?

Corey: Yeah, a little slower, yup, there you go,

There's the pace, yeah.

Akasha is our chief communications

And outreach officer.

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

Akasha: 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.

Corey: 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.

Akasha: How's it looking?

Corey: Looking good.

Akasha: Yeah?

Corey: There's actually a little anomaly

At the beginning of those stairs.

Akasha: Alright, I'm marking it right now.

Corey: Alright. Cool. Got the mark.

Akasha: Got it?

Narrator: The gpr immediately finds something.

Hints of a mysterious subterranean world rise up.

Akasha: We don't know exactly what's below there.

We get this nice, clear picture of voids or reflective spaces.

Corey: Alright!

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

Akasha: Let's go in!

Corey: Cool!

Try to bang that right up against the wall.

Just nice and slow, nice and slow!

(beep) cool.

Whoa, I'm seeing stuff, keep going.

(akasha 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: Chichén itzá...

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.

Corey: Whoa, I'm seeing stuff, keep going.

(akasha gasps)

Narrator: And using high-tech tools,

The virtual wonders team, alongside maya experts,

Are trying to find an entrance into it.

Corey: The biggest anomaly was definitely

On the entry over there.

Akasha: Ok.

Corey: We are indeed the first 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.

Akasha: Awesome.

Corey: Yeah, it seems like maybe three feet down or so

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

Or it might be like the base that they built on.

Akasha: Like the substructure? Corey: Right.

Corey: To be able to actually image what's beneath that floor

Is amazing.

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.

Akasha: 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. (laughs)

Kenny: 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.

Corey: I would describe kenny broad as 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.

Kenny: I don't wanna wait.

Memo: Alright, let's go!

Kenny: 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... Amazing room.

Kenny: Oh!

Memo: Here we are.

Kenny: Wow! Oh, my gosh, that's incredible.

Memo: Yeah, this is where the king use to sit.

Narrator: This is the jaguar throne.

Kenny: 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?

Kenny: And those are the original insets. Is that jade?

Memo: This is jade.

Narrator: To the maya, jade was a royal resource

Used to communicate with the gods.

Kenny: But there's no local jade, so.

Memo: Exactly, yeah.

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 the king used to rest and sit, it's also a funerary one.

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

Kenny: Resurrection. Memo: Resurrection.

Kenny: 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 what we see here, it's embedded bones.

They are long, long human bones that are embedded on the wall.

There's one there, another one here, and there.

My assumption as a bioarchaeologist,

I believe these are leg bones.

Kenny: Looks like it would be a femur or maybe...

Memo: Exactly, or tibias.

If you ask me I would say, yeah,

That might represent bones of ancestors.

Kenny: Right.

Memo: Or people very powerful.

Kenny: What's your sense of what could be behind this wall?

Memo: Well, I do really believe that there is something

Intentionally deposited there,

Given the sacredness of the site,

The importance of the place within chichén itzá,

I believe it could be a burial back there.

Kenny: I mean, it makes logical sense.

Memo: 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?

Kenny: I can feel the wind coming through here.

It's like you've...

Memo: Oh, yeah. You feel that? You feel that?

Kenny: Yeah.

Memo: That could be a caving system down there.

Kenny: No, and right, when we explore caves,

We look for that kind of breeze as a, it's a sign.

Memo: When we feel that breeze, it's, "let's go."

Kenny: Yeah.

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.

Kenny: Wow.

Memo: Or maybe an entrance. Kenny: Right.

Memo: And you can see some, some voids.

Kenny: 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 wonders headquarters,

Corey and akasha have processed their gpr findings

And discover something promising.

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

Right along the fence line, about about a half meter

From the fence line, and then this way and this way.

But what we're seeing here,

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, seems like there's a rock base,

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

So this is in the southeast corner of el castillo,

'cause this is between three and four meters deep over here.

Memo: Oh, wow, that's deep enough.

Corey: And there is what looks like a really strong return.

Memo: It looks like a very irregular cavity, right?

Corey: It looks, I mean, from a single gpr radar-gram like that,

Yeah, I would say that looks like a cavity.

Memo: So, like, a natural cavity, I mean?

Corey: 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.

Memo: How far actually from the corner?

Corey: It's almost exactly on the corner.

Memo: Ok, that's very, very interesting.

Corey: Yeah. Memo: Wow.

Corey: What I now want to show you,

Kash and I took the gpr in this 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.

Memo: Towards the center of el castillo?

Corey: Right.

This right here is the brightest radar reflection I've seen

Anywhere in chichén itzá.

Memo: It looks amazing.

Corey: I've been dragging this radar around.

This to me is a pretty clear void

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

Memo: Corey, I think this is amazing,

But what I think what amazes me even more

Is that both anomalies are the same depth.

Corey: Yup.

Memo: 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?

Corey: 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, "ok, 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.

Memo: Might have comparison.

Corey: Maybe, you know, I think it builds more meaning to me.

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 chichén itzá landmark: El osario.

El osario is also known as the tomb of the high priest.

Another temple on the grounds of chichén itzá,

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.

Memo: El osario kind of replicates

What we see in el castillo.

Corey: Yeah, it looks very much similar, yeah.

Memo: It's a radial pyramid, four access stairways,

Snakes, snake heads at the end, so the similarities are amazing,

Why not thinking there's a cavern also in el castillo.

Corey: Yup.

Memo: 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 a logical place

To find a passageway to el castillo.

Narrator: The question is do these underground passageways

Connect to the chamber beneath el castillo?

Corey: 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.

Corey: It's a set of mayan stairs, and they're super steep,

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

Like the stairs outside of el castillo.

Chris: Alright!

So, we'll connect this up?

Corey: Yeah, get it in there.

(speaking spanish)

♪ ♪

♪ ♪

Memo: We're looking for tunnels here.

Corey: Yes.

Memo: I want you guys to look for possible areas or gaps,

And see if there's a passageway behind.

Corey: 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 nobody has been here with technology.

Corey: Has used technology, right.

Chris: Yeah.

Corey: I guess they had 1800s technology last time they...

(laughter)

Chris: 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.

Corey: Robot, cable, tablet. Chris: Yeah.

Chris: Only three giant things, it will be fine.

Corey: Yeah.

Chris: I'm definitely the one sweating the most

If nobody's noticed.

Let's go! Let's do it!

Corey: Right! Memo: Ok.

Narrator: To get underneath el osario,

They must risk life and limb.

(speaking spanish)

Corey: 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.

♪ ♪

♪ ♪

♪ ♪

Jeez!

Chris: Corey's on the way down!

♪ ♪

♪ ♪

Corey: Right, coming down.

Not a lot of room, hey?

Memo: Not a lot of room, man.

Corey: What's the drop? Memo: 60 feet.

Corey: 60 feet. Yeah, cool.

But this is it. We're, we're crammed in here.

Memo: How dangerous this place is?

Corey: Yeah, man.

Memo: Any rock...

Corey: Yeah, you're dead.

Memo: ...And you're dead.

Woo!

Corey: 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've 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.

Chris: Alright, corey, borescope's on its way!

Narrator: The borescope has a small camera

That can snake around nooks and crannies.

Corey: Ok, so, I'm going to feed out the borescope cable.

Memo: Ok.

Corey: And, guillermo, so we'll have to straighten this out

So the borescope can articulate, so be careful.

Alright, memo, start going.

Go a little bit more in.

Yeah, we got something interesting.

Hey, look at this. What is this?

Memo: I think this is the original entrance to this cave.

Corey: Oh, right there. Right!

Memo: Yes.

Corey: Yeah. Oh, my god!

Narrator: But there's something even more intriguing

About this underground entrance.

The passageway has been mysteriously blocked

By something man-made.

Corey: Do you think they're cave-in,

Or do you think they were blocked by the maya?

Memo: No, no, I think it was the maya.

Corey: Right.

Memo: The ancient maya sealed it.

Corey: Ok.

Memo: It was like completely blocked.

Narrator: Memo believes the ancient maya did this

Because of where the passage points.

Corey: 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.

Corey: 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.

Corey: Oh, that's pottery?

Memo: Yeah, oh, yeah.

Corey: Wow, wow, hold on there for a second.

Memo: You see all the ceramic there?

Corey: Where? 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 sherds

Is even more mystifying.

Corey: 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.

Corey: The ceramic's on the ceiling?

Memo: Yeah.

Corey: You find pottery all over the floor of the caves

All the time, but shards of pottery, you know,

Hanging down like they could fall on you like knives

From the ceiling, and, you know, that's weird.

And that's the ceiling we're pointed towards,

Right, you said?

Memo: Yes, exactly.

Corey: That's crazy.

Narrator: What would have prompted the maya

To affix broken pottery to the ceiling

Of this sacred underground chamber?

Corey: Is it ritually sacrificed pottery?

Memo: Yeah, this is ritually sacrificed.

They used fire as part of their ritual.

It's charcoal, mud and ceramics.

Corey: Wow!

Memo: And then they mix it all together.

Corey: You think they filled this in,

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 weird.

Narrator: But why did the maya intentionally block

This underground tunnel?

Before they can investigate any further...

(thunder)

Chris: Ooh, boy, that's gonna be a big one.

Oh, (bleep)!

Lightning is probably my least favorite.

(thunder)

Narrator: An unexpected storm threatens

Not just the investigation, but the lives of the men below.

Chris: 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.

Hold on one second.

Corey: 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!

(thunder)

Narrator: At chichén itzá'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.

(thunder) chris: Oh, boy!

Corey: Let's go!

Narrator: But their search comes to a grinding halt

When lightning strikes.

Chris: 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.

Corey: Alright. Gracias.

Chris: There you go! Nice. Corey: Gracias.

Corey: People have died being hit by lightning.

We've got this big, metal frame around it

That's being used to lower people.

Ooh!

Man: How'd it go?

Corey: That was, that was crazy.

The lightning's just ripping down all around.

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

Man: Yes!

Corey: 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.

Corey: Basically, we put the borescope in

Everywhere it would fit.

Narrator: To help resolve this mystery,

Maya archaeologist dr. Jim brady joins the team.

Jim brady: That's really terrific!

Corey: The pottery's right here. Chris: Oh, is it that structure?

Corey: Those are all the shards there.

Narrator: Dr. Brady is one of the few archaeologists

Who have really explored the mysteries of el osario.

His expertise could yield crucial insight

Into this enigmatic blocked passageway.

Corey: 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.

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.

Corey: Ok.

Brady: We sampled that charcoal

And have gotten the radiocarbon dates back

That come out about, oh, 725, 728 ad.

Corey: 725? Wow.

Narrator: Traditionally, most scholars believed el osario

Was built in 980 ad.

But recent research is turning this notion on its head.

Brady: The osario was built much earlier than people think.

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

Corey: Really? Brady: Yes.

Memo: Wow, yeah, yeah, yeah.

Chris: How much earlier does that place it

In comparison to other buildings?

Corey: Like what's el castillo, do you think?

Brady: The castillo would be later,

And so this is gonna change everything.

Corey: Oh, wow! Yeah, yeah, yeah, yeah.

Brady: And this is gonna change everything,

Because rather than the osario being a model of the castillo,

It might be the other way around.

Corey: 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.

Kenny: Is this sort of the same idea

That how they packed everything off, closed something off?

Memo: Like termination ritual, you mean?

Kenny: Exactly.

Memo: What you think, dr. Brady?

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.

Akasha: That's crazy! Corey: 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'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 chichén itzá 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 the 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 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 underexplored 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 chichén itzá,

Virtual wonders and maya archaeologist guillermo de anda

Are making their way to one of the four major cenotes

That surround chichén itzá'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 a passageway that goes who knows where.

Memo: Ok. 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.

Corey: You good, chris? Chris: Yeah.

Corey: Alright. Chris: Ok.

Narrator: Corey and memo will scuba dive

To look for any concealed passageways.

Chris: Ok, 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?

Chris: 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.

Ok!

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 you're able to see it.

Corey: Is that you? Chris: Yep, that's me.

Corey: Alright, go.

Cool. Props are turning.

There you go. You have video?

Chris: Yep.

Corey: Alright!

Are you on the slowest mode possible?

Chris: I'm on the slowest mode possible.

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

Corey: Ok.

Chris: Have a good dive, man.

Corey: Yeah. Thanks, buddy! We'll see you soon.

Chris: Go find something.

Corey: 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.

♪ ♪

♪ ♪

Chris: I apologize for being silent.

I'm just, I am so intently focused.

Corey: But being able to have a talented rov pilot

Maneuver it through to see where that passage goes,

It'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.

♪ ♪

♪ ♪

♪ ♪

Chris: Oh, oh, oh.

Come on.

Come on, baby! Keep moving.

My mom said that video games weren't a career.

♪ ♪

I'm definitely seeing stuff.

Wow! This is beautiful.

We found a new cave.

I am, I'm pretty wildly excited right now.

I think this keeps continuing.

Narrator: At the iconic chichén itzá,

Virtual wonders and memo de anda

Have found an undiscovered, underwater passageway...

Chris: I'm definitely seeing stuff.

Narrator: ...That could lead to a hidden chamber

Below el castillo.

Chris: Wow! This is beautiful.

♪ ♪

We found a new cave.

I am, I'm 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.

Corey: 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 cave and to go make offerings.

Chris: Ok, let's turn.

♪ ♪

♪ ♪

We're definitely in a large passage

That 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 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.

I'm really hoping not to disturb anything,

So I have to be really careful,

But this is spectacular, 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?

Chris: It definitely goes.

Corey: In cave terminology we know that that passage "goes,"

Meaning that it continues on past what we can see.

Corey: How big did you think the passage was?

Chris: It could be 10 to even 30 feet up, I mean, it was tall.

It's hard to get scale on this video,

So before, you know, I make a grand claim,

But it was big enough to fit a person definitely,

And it looked like it went up pretty tall.

Corey: Wow!

Chris: We'll have to review the video, though,

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

Corey: That's awesome!

Memo: These passageways never go straight.

Corey: Right.

Memo: I mean, very seldom.

Corey: This one definitely doesn't.

Chris: This one didn't go straight,

This one went up, left, right and down.

It could have gone in any direction, absolutely.

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

Memo: We found a passageway.

Corey: Really successful dive.

Gracias. Alright.

Anytime you do a dive with a bunch of new technology

And you come back with all the technology

And everything looks like it worked...

Man: Yeah.

Corey: It's a win, right? Memo: (laughs) oh, yeah.

Chris: 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 chichén, but chris said it's...

Corey: It bends.

Chris: 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.

Chris: Alright, 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 was a hard one.

Corey: No one's ever been back there, right, memo?

This is unexplored caves?

Memo: No, no, this is completely unexplored.

Chris: 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 huge compared to the crevice

That it actually started at, you know?

Memo: Yes. Yes, yes. Corey: Yeah. Right, right, yeah.

Chris: Look down here.

You've got a passage that comes here

And it also goes in this direction.

Corey: Wow!

Narrator: Though they can't tell if the passageway

Ultimately extends to the potential cenote

Below el castillo, they do collect important evidence.

Chris: So, zoom it back just a little bit.

Corey: Zooming it back.

Chris: 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.

Corey: Oh, (bleep)!

Hey, hey, hey, hey, memo! What is that?

What is that green bit right there?

Memo: Oh, yeah? Chris: Oh, man!

Akasha: Oh, my god!

Memo: Looks like a jade bead.

Corey: That was jade.

Narrator: Jade.

Memo: Wow!

Corey: Yeah, totally.

Chris: Wow!

Narrator: In the ancient world of the maya,

Jade was a royal resource and a precious commodity

Used to communicate with the gods.

Corey: That's an offering, yeah.

Chris: 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.

Corey: I would suspect when there's the worst droughts,

There were 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.

Memo: There's another one. Chris: Yeah.

Memo: This one, look, this, this. Wow!

Narrator: These offerings may have been a last-ditch appeal

To the gods to save the city of chichén itzá

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 chichén itzá,

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.

Captioned by side door media services