Original subtitles

Hidden from human eyes.

Mysterious tombs,

where mourners could speak directly to the dead.

And caves filled with giant crystals

that are as beautiful as they are deadly.

For centuries, mankind has wondered,

what lies deep beneath our feet?

Is there a subterranean world filled with mystery and danger?

Or one that hides untold riches?

Perhaps even the secrets of the universe?

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

Bordered by the Black Sea to the north

and by the Taurus Mountains to the south,

lies the craggy regions of Cappadocia.

Here, wind, water, and time have sculpted the volcanic rocks

into bizarre and almost surreal shapes.

But believe it or not, the most unusual thing

that was ever discovered in this otherworldly landscape

was found not above ground, but far below.

In 1963, during a simple home renovation

in the town of Derinkuyu,

a cave wall was punctured, revealing a passageway

to what appeared to be an intricate underground city,

thousands of years old and more than 280 feet deep.

Derinkuyu is a pretty amazing story,

'cause just imagine that you're working

in your basement one day.

You knock a hole in the wall,

and what you find is a city that is,

it's sort of the size of a‐a really large castle,

but it's actually underground.

Uh, and it was done in a time

before there was really any mechanical means

to provide water or ventilation,

or any of those things.

The only thing on the surface that you can see

are what appear to be wells.

As you approach Derinkuyu,

you would certainly not be aware

that you were walking over the position

of an underground city.

It would have been the home for thousands of people

at a time at some point in the distant past.

Home to thousands?

It seems hard to believe that an entire city

could actually exist underground.

And yet, experts claim that Derinkuyu housed

an estimated 20,000 men, women, and children

and included religious centers, storerooms, and living rooms.

But how?

Derinkuyu appears to be a combination of

leveraging natural cave systems,

and then building in human technology to connect it.

And one of the things that's fascinating about this

is the ventilation system,

because here you're really just worried about getting air in,

and waste like CO2 and air out.

You're gonna be able to store water.

If you think about how much fresh water

is already naturally underground,

we're constantly digging down to get to wells,

but if you're already underground,

the wells are right there.

So you have the possibility of great fresh water sources.

Many archeologists and scholars

claim that Derinkuyu was most likely built

around 800 BC by the Phrygians,

a Bronze Age people related to the Trojans,

and was intended to serve as a temporary shelter

from invasion.

But others believe it was built by the Hittites,

a warrior people mentioned in the Bible,

who flourished a few hundred years before that.

This is in a place that's had multiple wars.

There's conflict taking place all the time.

And when you're above ground,

people can see you for miles.

You know, each night you're lighting fires

to get some light inside the space.

And so, that can be seen from 20 miles or more.

Once they go below ground, they're invisible.

It has, uh, massive stones that can be lowered

to block passageways that human beings

can only go through in single file,

making it very easy to defend.

There are also rumors that it is connected

by a vast tunnel system going many, many kilometers

to other underground cities in the neighborhood.

So, it had emergency escape routes.

So the whole thing was a quite remarkable

subterranean fortress.

While there is evidence to suggest

that several different cultures have used Derinkuyu

as a fortified sanctuary

in the centuries that have passed

since its initial construction,

some researchers have theorized that it is much, much older

than mainstream archeologists think.

And that its original architects

had an even bigger threat in mind when they built it.

The curator of Derinkuyu in Cappadocia,

Omer Demir, had found the evidence suggesting

that each of the different stories or levels

would seem to have been constructed

by different cultures at different times.

And what he found was incredible.

For he discovered that there were tools,

stone tools here, that dated back

to Paleolithic times.

The implications of this are enormous,

because what this suggests is that Derinkuyu goes back

at least 12,000 years,

and was present at the end of the last Ice Age;

and may well have been a place where our ancestors

sought refuge at the time of a cataclysm,

a cataclysm that may well have devastated

large parts of the Earth

at the very end of the Paleolithic era.

A cataclysm?

Could it be that the original inhabitants

of Derinkuyu built it as a shelter to protect them

during the Earth's last great Ice Age?

A time when the Earth's climate was estimated to be

more than 10 degrees colder than it is now?

So cold that hardly anything could grow,

or even survive, above ground?

When you build your city underground,

you get two major off‐the‐top advantages,

one sort of environmental.

You're gonna have great thermal properties.

It's gonna be cool when you need it to be cool,

but it won't get too cold,

so it'll be kind of warm enough when you need it to be warm.

Thinking about when this was built and inhabited

really remains this exciting, mysterious, open question.

Even this idea of other cities underground,

like, how common was that

for humans to build their homes underground,

versus on the surface of the ground?

Derinkuyu was rediscovered

during the 1960s by accident.

And there are still areas of it

that have not been explored to this day.

So the implications of this are incredible.

It does feel like we've just really

scratched the surface of what could be below us.

There could be much more.

There could be many more of these cave systems in Turkey.

So there's mysteries still to be found

deep within the Earth.

The truth is, we may never know for sure why,

or even how these ancient underground cities were built.

And that's especially true in the case of Derinkuyu;

because the secrets of its construction techniques

seem to have disappeared, along with whoever built it.

Even today, with all of the modern technology

that we have, it would be incredibly complicated

and a massive undertaking to do something like that.

And sometimes, we look at these ancient marvels,

and we try and figure out, could we build that today,

to that level of accuracy,

that sort of quality of construction

in that amount of time?

And the answer's no, which is pretty amazing

that several thousand years later, they're better than us.

Is it possible the builders of Derinkuyu

knew something we don't?

Not merely about constructing cities

deep within the Earth,

but about humanity's need for such refuges

in order to survive?

It's a fascinating, and perhaps, slightly unnerving prospect.

Not unlike another underground structure,

one that exists in order to maintain communication

after the end of civilization itself.

In the event of an attack, it's believed the United States

it's not difficult to believe the United States government

has a closet full of secrets.

But what could be so secret that they feel the need

to keep it hidden so far underground?

Area 51 is the world's most secret installation.

Historically, we know that it was used

for the testing of early spy planes,

like the U‐2 and the SR‐71 Blackbird.

A number of whistleblowers have come forward

claiming to have seen levels up to about

seven or eight levels, um, deep below the desert,

protecting whatever's really going on at Area 51.

If there are these large tunnels and pathways under Area 51,

so many people would have to cooperate in building it

that'd be difficult keeping it a secret.

But you could also ask the question,

when was the last time you paid any attention

to a new subway tunnel being, uh, constructed

under the city in which you live?

You probably never paid attention to it.

So, it could be built right under your nose

and you would never know it‐‐ or care, for that matter.

Deep beneath these snowy peaks,

encased within thousands of tons of solid granite,

lies the most sophisticated and impenetrable

military installation in the world.

The Cheyenne Mountain Complex was built, uh, in the '60s

and was operational in 1967.

And the idea was that you have all of your information

for our national missile defense

and offense capabilities to be operated from there.

So it had to be able to withstand major natural

and man‐made disasters such as a nuclear attack.

So, the Air Force and Army and Navy,

all of the services, they were in there.

Basically, it was the nexus of our Cold War defense center.

The Cold War was at its height, and for that reason,

it demonstrated why we had the need

to have these kind of facilities deeply below ground,

to allow them to hopefully survive a nuclear attack

if the worst scenario ever happened.

Originally built for a staggering cost

of almost $150 million, or over one billion today,

the Cheyenne Mountain Complex spans an incredible five acres

and contains 13 three‐story buildings

capable of housing up to 2,000 personnel,

independent power, heating and cooling systems,

a lake that serves as a reservoir

and 25‐ton blast doors capable of withstanding the force

of a 30‐megaton nuclear explosion.

If there was a nuclear attack, a direct hit,

Cheyenne Mountain was deep enough

that you would not be dry‐roasted.

You would survive the heat.

Then you got gamma rays and radioactive fallout,

but the best protection is material.

Dirt, earth, rocks.

All these things are gonna protect you from that.

The Cheyenne Mountain Complex

was so central

to the United States government's survival plans

that they eventually realized

it may not actually be a good idea for it to be so isolated.

Let's say, in a worst‐case scenario,

that Washington D. C. gets taken out by a nuclear weapon.

Well, one of the theories is that the president and all

of his staff would quickly be taken to the Denver Airport.

The Denver Airport not being too far from Cheyenne Mountain,

it would make great sense to have a tunnel rail system

deep below the nation which potentially could go

from Cheyenne Mountain straight through to the Denver Airport.

When they were building that airport,

there was this massive‐‐

and I mean massive‐‐ hole in the ground.

And buildings were going up in there.

Buildings that, all of a sudden, you know,

you‐you didn't see them when the airport was finished.

And their answer to that was, "Well,

"the buildings were incorrect, and we had such a big hole,

we just covered them over and kept building."

W‐Who would buy that?

When the airport was being constructed in 1995,

some of the staff who were working on the facility itself,

construction staff, engineers,

they claimed to have seen what appeared to be

large tunneling devices, and also, large tunnels,

which shouldn't really have been there.

A lot of people theorize that there is something to this deal

about Denver Airport because an airport

is an extremely secure location on the surface.

You can't just walk in and go anywhere you want.

That's good if you're hiding stuff underground.

Could the United States government actually be operating

a top‐secret tunnel system whose epicenter is beneath

one of the largest transportation hubs

in the country?

According to some experts, the answer is yes.

And that may only be the tip of the proverbial iceberg.

For strategic means, it's believed the United States

has numerous underground facilities

which, essentially, have been bored out

with these gigantic boring machines to create tunnels

to essentially take people all across the United States

in the event of an attack.

We're talking about trains deep under the surface

to essentially go from the east coast to the west coast

to the north to the south

to hide from the attacks that might be going on.

There has been a great advance, just in civilian

and openly‐known abilities to dig tunnels.

This is being taken advantage of by Elon Musk

and his Hyperloop concept, that we can create

long‐distance underground transportation systems.

So we can only imagine what has been accomplished

in the secretive world of the U. S. military.

But as profound and disturbing as is the notion

of a vast network of underground bases and secret tunnels,

there are some underground worlds that are formed

not by man but by nature.

And in at least one case,

the formation is so beautiful

that it's easy to forget that, just like mankind,

Mother Nature can also be deadly.

Fin the mineral‐rich towne gotten aof Naica, they are,

more than 1,000 feet below the surface of the Earth,

a group of miners drilling through a cave wall

make a remarkable discovery.

Not of precious metals,

but something far more wonderous and mysterious.

A glittering cavern, untouched for half a million years,

filled with the largest crystals ever found.

It's amazing.

There are crystals that are huge.

So big you can actually walk across them.

And for these crystals to have gotten as big as they are,

they had to have been growing for hundreds

of thousands of years.

It's a fascinating location.

This is something you would think would only exist

in the world of science fiction and fantasy,

but the fact is, it's all too real.

Measuring up to an astonishing 40 feet in length

and weighing as much as 55 tons, the giant beams

are the purest form of selenite crystal in the world.

Crystals are the most orderly structure in nature,

and they have the ability to absorb frequency and energy

from objects around them.

Now, it is my theory that these giant pylons have the ability

to transmit and receive information and light.

Only a few months after its discovery, a team of scientists

was sent in to study this geological anomaly.

They soon learned that Naica's Crystal Cave may be

not only beautiful but deadly.

It's 90% to 100% relative humidity inside this cave.

And it's always over 113 degrees Fahrenheit.

You might think, "Well, 113 degrees isn't that bad.

"It gets 140 degrees

in the deserts in Iraq all the time and people live there,"

but the relative humidity in those deserts is 10%.

In this cave, there's so much humidity,

you can't sweat and cool your body off.

I received an invitation to go

on an expedition and exploration of these giant crystals.

I was aware of the heat and humidity,

but nothing prepared me

for what hit me when I entered those caves.

I felt like I was hit by a tsunami

of tremendous heat and humidity.

I started shaking, I was scared.

These are near‐fatal conditions.

Due to the Crystal Cave's lethal atmosphere,

the research team was restricted

to ten‐minute exposures to avoid being cooked alive.

For gemologist Leela Hutchinson, the most unexpected discovery

wasn't something she saw but something she heard.

One of the things that I realized as I had to focus

so intensely to keep my wits about me,

was this ability to hear a low hum.

And I thought that was very strange.

I didn't know if it was the machinery

that were in the tunnels

or if it was something that might be in the cave itself.

And later I realized, could this have been

extremely low‐frequency resonating in there?

Nikola Tesla was quoted as once saying

that "we may not understand the growth of a crystal,

but nonetheless, it is a living being."

Energy from living, giant crystals?

In an attempt to navigate the unusual properties

of the crystals within the Naica cave,

NASA developed special cooling equipment

allowing scientists to withstand the cave's lethal conditions

for as much as 30 minutes at a time.

And according to their research, the hum emanating

from the Crystal Cave may not be because its crystals

are storing energy, but because they're harboring

life.

In the 2008 expedition, the NASA scientists

went into the caves and drew out fluid inclusions

in the largest crystals,

and found microbes that are considered to be extremophiles.

Microbes that are living organisms.

They're single‐celled, and they have the ability

to survive and thrive in extreme environments.

One of the interesting things about the extremophiles was

there is nothing in our genetic database

that comes close to what these extremophiles are.

Microbes unlike anything seen on Earth.

NASA's astrobiology report suggests these extremophiles

are up to 50,000 years old,

and could survive on other planets.

Is there a risk involved in handling

these never‐before‐seen organisms?

The Cave of the Crystals can be a dangerous place.

For example, not long after it was found,

one of the workers actually snuck back into the cave.

Not surprisingly, he passed out and died.

Now, it's unclear if he died from the air quality,

the heat, the humidity.

Or could it have been the extremophile microorganisms

that were in there?

Will we ever find out whether the giant crystals

in the Naica cave hold the key to understanding

the origins of life?

Or is this one underground mystery that is simply

too dangerous for us to investigate?

Perhaps.

But not all underground worlds are meant to help us understand

the mysteries of life.

Some actually appear to be constructed

to bring us closer...

to what happens to us after we die.

While excavating an area It's extraordinary.

For a new housing development

just off the eastern coast of this tiny Mediterranean island,

construction workers encounter something unexpected

and quite unusual beneath their work site.

A prehistoric structure, hewn from solid limestone,

dating back more than 5,000 years.

Upon further inspection, archaeologists soon realize

that what the unwitting workers have unearthed

isn't merely a lost underground temple

or ancient sanctuary,

but a massive subterranean necropolis.

The Hypogeum of Hal Saflieni.

The Malta Hypogeum is an architectural wonder

of the ancient world.

It was carved using primarily stone and bone tools

by an ancient population that lived on Malta

thousands of years ago.

So, it's actually older than the pyramids of Egypt or Stonehenge.

"Hypogeum" is basically a word that comes

from the Greek terms for "cavity" or "space underground."

It extends on three different stories

about seven‐point‐some meters below ground.

It covers an area of about 5,400 square feet.

Malta's Hypogeum is, you know, one of those great examples

of, uh, beautiful geometry, uh, underground.

So, the geometry isn't by accident.

It was done by somebody who knows what they were doing.

And it looks to me, like,

you know, this was done for a purpose.

A purpose?

Although no one knows for certain who originally built

the Malta Hypogeum or why,

the bones of more than 7,000 souls

line its intricate labyrinth of corridors and alcoves.

So, according to logic,

it is exactly what it appears to be: an ancient burial site.

But logic alone may not be at play here.

There is a very intriguing room in the Hypogeum,

which is in the middle level, uh,

that is called the Oracle Room.

And this Oracle Room is basically a resonance chamber.

And it's designed, so it would seem,

to amplify any acoustic sound waves.

So, even by whispering, for example,

uh, the design of the room amplifies this

and‐and makes it into a very loud baritone sound.

The Oracle chamber itself

appears to have been carved specifically

to allow sound frequencies to travel,

and the ceiling of the Oracle chamber

actually appears to have been carved to direct sound.

There are also niches that have been carved

in the sides of the Oracle chamber that seem

to be a way to produce echoes and were also created,

in a way, to tune it to the right frequency.

So, there was a sophistication there

that, you know, is unexpected.

In 2014, while conducting a series of experiments

in an attempt to understand the design elements

behind the Hypogeum's unusual acoustics,

scientists discovered

an unexpected and hair‐raising phenomenon.

We set up microphones and we used recording devices

that were very sensitive, and we carried out experiments

using the human voice in that 110 to 112, uh, hertz range.

So, these are very low, guttural, bass sounds,

and they reverberate in a very strong way within these temples.

I‐It's extraordinary.

It's like being inside of a bell.

And those vibrations are felt inside your body.

You feel it in your tissue, you feel it in your bones.

It can raise the hair off the back of your neck.

Imagine going there to this dark and spooky underground place

5,000 years ago, with this weird, eerie sound

going on around you and‐and knowing that there are bones

and‐‐ the whole thing is creepy now.

It clearly was‐‐ some sort of ritual activity went on there.

There is a niche in the Oracle Room,

that if you spoke into it, it could resonate

throughout the whole structure.

And so, some thought it was significant,

that a priest might've intoned into it a voice‐‐

that his booming voice would go through the whole Hypogeum.

Uh, like a god.

The voice of a god?

Those who have visited the Malta Hypogeum

describe it as feeling like a descent

into the underworld.

As a result, some experts believe

this subterranean nightmare was intentionally constructed

to enable its visitors to speak with the dead.

Overtone chanting is a common practice

in many cultures in, uh, East Asia,

and, uh, North Asia and South Asia as well.

You do have this strong connection between chanting

and communication with the divine or with the deceased.

And I believe at the Hypogeum, we may have a similar situation

in which there seems to have been an active ritual function

of, uh, not only placing the deceased or remains there,

but where people would attempt to establish communication

with the dead.

In the range of 110 to 112 hertz is a frequency that, uh,

has a specific effect on our brain.

It puts us in a sleep state and has us producing alpha waves.

What happens when the alpha waves are produced

is that it kind of quiets the, um, language center of our brain

and puts us in more of a meditative or trance‐like state.

It's similar, in many regards, to what happens, uh,

when a shaman uses the practice of ingesting

psychoactive chemicals, whether it's ayahuasca

or whether it's, uh, mushrooms of some type.

So, it stands to reason that, potentially,

people could attain a different level of consciousness

in which they would be susceptible to have experiences

of communicating with the dead or with the divine.

As far‐fetched as the notion

of communicating with the dead may seem to us,

some believe whoever built the Hypogeum

may have been on to something.

Because it appears they left behind instructions.

There is this spiralic painting

on the ceiling of the, uh, Oracle Room.

And it's not unusual to use spiralic shapes in prehistory

and early times to represent‐‐ visually, graphically‐‐

represent sound in terms of spirals.

So it was clearly an intellectual connection.

The clues may lie right before our eyes.

Those sounds, those songs, those tones, those frequencies

that were played and heard

were of the utmost importance to them.

We don't understand exactly why.

But by studying them, hopefully, we can shed some light

on not only what they were trying to do

but how we could use those same concepts,

those same understandings,

to perhaps benefit our society today.

An ancient necropolis

constructed and designed

to allow people to send messages

into the afterlife?

Fascinating...

albeit a disturbing concept.

Not unlike one of the most persistent and bizarre theories

about our planet.

The notion that it could be...

hollow.

Acclaimed novelist whJules Verne publishest.

The science‐fiction novel

A Journey to the Center of the Earth.

The book‐‐ which chronicles an adventure

through a fantastical subterranean world

filled with mammoth creatures,

underground oceans,

and crystal caves‐‐ is an instant success.

But despite Jules Verne's insistence that the story

is nothing more than a work of fantasy,

many wondered...

could some of what he wrote

actually be true?

We live on the surface of planet Earth,

but going back many thousands of years,

we have wondered what is beneath our feet.

Is it solid?

Or is it possible that it could be hollow?

One of the most fascinating people

in the history of science is Edmond Halley,

who Halley's Comet is named after.

Based on his explorations,

he discovered the Earth's magnetic field was fluctuating,

that it was not a steady, uniform object.

It was changing in time.

It appeared to be kind of rotating

relative to the surface of the Earth.

So he came up with a quite elaborate model

to try to explain what he was seeing

in his measurements of the Earth's magnetic field.

And one of the interesting theories he came up with

was the idea of a hollow Earth.

Edmond Halley

believed there were essentially three crusts‐‐

three rotating crusts which surrounded this huge,

hollowed‐out portion of planet Earth.

A hollow Earth?

Is it possible that there's actually another world

located deep within the Earth's crust?

Could Jules Verne's fantastical notion of a subterranean world

located deep underground have been based

not on mere imagination

but on scientific fact?

Well, if one legendary explorer is to be believed,

the answer is yes.

And he claimed to have even seen it firsthand.

Rear Admiral Richard Byrd,

in essence, was somebody who we could equate

with, like, a real‐life Indiana Jones.

He traveled around the world

having expeditions and adventures.

He was someone who visited

the polar areas, which really fascinated him.

And in 1926,

while flying over the caps,

he was able to see what he described

as like a large green valley.

One of the ideas about this whole hollow Earth theory

is that there were multiple entrances all over the world.

But most notably, the North and South Poles

are possibly the entrance for these.

According to the story,

Byrd described massive forest areas

nurtured by some kind of sun

deep inside the planet itself.

And he claimed to have seen, uh,

a fully grown woolly mammoth,

which it would be amazing if that was true.

Underground rivers,

extinct mammoths and a sun deep inside the Earth?

Could the incredible account of Admiral Byrd‐‐

one of the world's greatest explorers‐‐

actually be true?

But if so,

where's the evidence?

There's water on the surface in huge oceans.

What if there's a hole in the mantle

that allows some of it to drain somewhere?

Did it get captured there

when the Earth was created in its formation?

I'll give you an example.

In Mammoth Cave in Kentucky,

there were the remains of a shark

from 330 million years ago.

An extinct creature found in this cave,

in a cave‐‐ not in an ocean but in a cave.

What if this cave was part of an ocean system

that went deeper underground?

As a scientist,

the first thing I will concede,

is that we do know there are vast caverns below us,

and there are vast structures that are dynamic

under the Earth.

And so it's certainly possible.

The Earth is about 7,000 to 8,000 miles in diameter.

That's pretty big.

We've only ever drilled to about eight miles deep.

We have no idea what's at the center of the Earth.

You know, we have theories that there's this molten ball core,

iron core spinning around, it's magnetized or whatever,

but we really don't know.

There could be a completely different world

that we just don't understand yet

because we've never been there

to do experiments and science on it

and understand what's going on.

If another world does exist deep beneath our own,

is it possible we might be able to one day access it?

There are those who believe that not only is the answer yes,

but that humanity's very future may lie

not above ground but down below.

As proof, they point to a village in China

where thousands of people

are already living deep underground.

In the rural region of Sanmenxia

lies an ancient network of villages

that exists entirely underground.

Millions of people have lived and worked here

spending their entire lives

beneath the surface for generations.

And not just thousands of years ago,

in the ancient past...

but to this very day.

Over the past 4,000 years

there were tens,

if not hundreds of thousands of people

living within these underground

dwellings in the northern part of China.

And these places, which are known generally

as yaodongs,

continue to be built even to this day,

and, in fact, the modern examples

created over the last hundred years

have got bathrooms, they've got electricity.

If you could imagine a sort of

modern‐day housing development anywhere in the world,

everybody had a basement and you took all of the houses away,

and all you were left with was the basements...

that's what Sanmenxia looks like.

It's these sort of rectangular

holes in the ground, like a chessboard,

all over the place.

There are many living options

in the underground dwellings of Sanmenxia,

ranging from simple one‐bedroom caves...

to more elaborate three‐bedroom homes

with modern appliances and plumbing.

But why would anyone choose to live below ground

in a country with several thriving cities to choose from?

One of the benefits of living underground,

especially in very hot and cold climates,

is below the earth, the temperature is more moderated,

so you don't get the extremes so much.

You know, it's probably pretty cool

most of the time and so,

you know, they're not bad places to be.

It could well be that with the expansion

of population at the rate that it is today

that going underground

is something that we should look towards in the future

to solving the problems of housing

and creating new cities.

You have to wonder, is the day gonna come

when the Earth itself,

at least from the perspective of the surface,

that the Earth simply will not

be able to stand any more people.

So what's the answer?

Maybe the answer is that we all move underground

or possibly a significant percentage

of the population choose to go underground.

Given everything going on in the world today,

will we live to see the day when our civilization

goes back underground?

It certainly seems safer.

And if that comes to pass,

will we then learn about all the other secrets

the Earth is hiding beneath its surface?

It seems that the answer will be one

that for now remains buried,

and... unexplained.

Subtitles Diego Moraes(oakislandtk) www.opensubtitles.org