All language subtitles for The UnXplained Special Presentation S01E19 1080p WEB h264-EDITH_track3_[eng]

WILLIAM SHATNER:
Secret military bases,

built deep underground.

Intricate cave systems

that were never meant
to be discovered.

And an arctic expedition
to the center of the Earth.

What is it
about a tunnel or a cave

that piques our interest?

Is it curiosity
about what the dark

and narrow passageways
may lead to?

Or could it be
the inherent danger

that comes
with being deep underground?

For centuries,

mankind has explored the depths
of the Earth,

and found not only
natural resources,

but what might be considered
a perfect hiding place.

Could the stories
of secret technology,

lost cities and hidden treasures
lying beneath our feet be true?

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

♪ ♪

As any fan
of spy movies will tell you,

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,

deep below the desert,

protecting whatever’s
really going on at Area 51.

TRAVIS TAYLOR:
If there are these large tunnels

and pathways under Area 51,

so many people would have
to cooperate in building it

that it’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 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.

SHATNER:
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 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, 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.

REDFERN:
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.

SHATNER:
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.

TAYLOR:
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 going
to protect you from that.

SHATNER:
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.

REDFERN:
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."

Who-who would buy that?

REDFERN:
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.

SHATNER:
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.

REFERN:
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

in 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.

SHATNER:
It’s not difficult to imagine

that in certain
doomsday scenarios,

the governments
of the world would prepare

fail-safe, underground tunnels.

And it appears
the defense capabilities

and anonymity
of moving underground

is not a modern concept.

Because there are caves

high in the Andes mountains
that not only concealed

an ancient civilization but also

their hidden treasures.

SHATNER:
In the eastern part of Ecuador,
not far from the border of Peru,

is the entrance to a cave

known as Cueva de los Tayos,

or the Caves of Tayos.

Located at an elevation
of 2,600 feet,

this winding cave system

contains a network of tunnels
approximately three miles long

and is considered sacred

by the native Shuar people
of the region.

But what’s most remarkable
about these caves

is that somewhere
within its depths

is believed to be a tomb
that was constructed

by a mysterious
lost civilization.

The Tayos Caves are arguably

one of the most enigmatic
cave systems in the world.

They first came to note
in the 1960s,

when an explorer
by the name of Juan Móricz

came suddenly out of the jungle,

claiming that he’d descended
hundreds of feet

into the Tayos Caves

and had seen incredible things.

This included

this tomb chamber
that is supposed to contain

evidence of a lost civilization.

Most particularly,
what he described

as a "metal library,"

of these metal tablets,

seemingly in gold,
with these weird glyphs

written all over them,

that were carved
by some kind of ancient race

that has been
entirely lost to us.

And Juan Móricz claimed

that this is what
he’d seen and wanted

to tell the world about this.

SHATNER: A metal library
containing gold tablets?

Juan Móricz’s
extraordinary account

sparked worldwide curiosity,

and many began to wonder
whether there really were

ancient gold tablets
hidden somewhere

in the Tayos Caves.

COLLINS:
Anybody reading that story

would have been fascinated by
the mystery of the Tayos Caves.

And this is, indeed,
what happened,

because it attracted
the attention

of a Scottish civil engineer
by the name of Stan Hall,

who decided that he would create

an expedition
to explore the caves.

SHATNER:
In 1976, Stan Hall recruited

a number of people
to join his expedition

to the remote jungle of Ecuador
in search of the gold tablets,

including American astronaut
Neil Armstrong,

whose participation
helped to draw

worldwide interest
to Hall’s efforts.

MUÑOZ:
My father became very obsessed

with this treasure story.

The expedition

that he mounted is still today

one of the largest of all time,
and it’s because it involved

over a hundred personnel
from both the British

and Ecuadorian governments’
special forces,

and some universities
sent their scientists.

The main challenge
was entering the cave,

because the only way to get in

is this very deep hole
in the ground.

SHATNER: According to
Stan Hall’s account

of the expedition,

the entrance to the Tayos Caves
was a hole

that required the group
to descend one by one

more than 200 feet.

Soon after
they entered the cave,

they made
an extraordinary discovery.

DAVID KUSHNER:
They saw these walls

leading from one chamber
to the next that looked smooth,

and they looked like
they’re cut at right angles.

So, it looks like the ruins
of some lost civilization.

SHATNER:
The massive walls did not
appear to be formed naturally,

but instead, they looked like
they were carved and placed,

as if they were man-made.

Stan Hall and his team
believed that this was evidence

that a lost civilization
had inhabited the Tayos Caves.

As they moved deeper
into the caves

in search of the gold tablets,

they made another
remarkable discovery

inside a chamber
they referred to

as the Altar of Light.

MUÑOZ:
Inside the Altar of Light,

there was a ray of sunlight
that shone

straight into the entrance
of that chamber,

and it made it
really significant.

And within it,
there’s a smaller chamber

in which my father’s expedition
found the remains of a person.

COLLINS:
They found this human skeleton,

and surrounding it

was pottery, um,

various shell objects
and adornments.

But unfortunately,
when they reached out

to touch this skeleton,

it fell apart,
it just fragmented,

showing how old it was.

But subsequent research

would show that this was
around 3,500 years old...

...dating back to 1500 BC.

And according
to the local Shuar,

this was one of their ancestors,

the race that had inhabited
the caves before them.

SHATNER:
The discovery
of this ancient tomb

was an astonishing
and unexpected find,

one that heightened the mystery
of who inhabited the Tayos Caves

and led many to wonder what else
might be hidden

within this vast network
of underground passages.

A few interesting things
happened

during Stan Hall’s expedition.

They did not find
the metal library,

but they did find other things.

Number one, it had these walls

that were cut at right angles,

and number two,
they found a corpse

that was dated
to go back to 1500 BC.

So, even though they didn’t
find the metal library,

Stan was still convinced
that it was there somewhere.

SHATNER:
An Altar of Light pointing
to a bejeweled ancient skeleton.

It’s certainly
a remarkable image,

one that would seem like
it came from the pages

of a harrowing
adventure novel, and yet,

it exists deep
in the Tayos Caves.

But where are
the golden tablets?

Perhaps clues can be found
by exploring another cave

from an ancient civilization
whose main purpose

was to never be found.

SHATNER:
In a small village,

a group of farmers
begin draining several ponds

to create space
for new planting fields.

But as the waters recede,

they make
a remarkable discovery.

CLEMENTS:
The villagers

saw the water
was slowly going down

and there were steps going down.

So, they got very excited
that this was some kind of,

you know,
archaeological discovery.

And when they went inside,

they found that they were
in a group

of underground man-made caverns.

SHATNER:
Once the water
was completely drained,

the villagers discovered
a series of astonishing chambers

that had been carved
underground centuries earlier.

Further excavations
revealed the existence

of 24 massive caverns.

Each cavern covers an area

of approximately
11,000 square feet,

or roughly the size
of two mansions.

Archaeologists have also noted
that the walls, pillars

and ceilings of the caverns
were all precisely carved

to have an unusually smooth
and symmetrical appearance.

All told,
the massive underground complex

measures 320,000 square feet,

which is the size of more
than five football fields.

These incredible
man-made structures

are collectively referred to

as the Longyou Caves.

The discovery
of the Longyou Caves

is very fascinating

because there was
absolutely nothing to suggest

that there were these
carved, beautiful caves

actually beneath the water.

And so, when the actual caves
were discovered,

everybody was absolutely amazed,

because there was no indication
that they existed.

They have these pillars
inside them

which are anything
up to 100 feet in height,

and there are long corridors,

there’s some beautiful
relief carvings on the walls

of animals and dragons,
and things like this

that are of immense
sophistication

in their design and the manner
that they were carved.

NEWMAN:
When you look at these carvings,

the chisel marks are so uniform,

there’s very detailed shaping
of some of the stones.

To the untrained eye,
it looks like something

created in the last
20 or 30 years.

Some people suggest the caves

are one of the wonders
of the ancient world,

but they weren’t
discovered until 1992.

So, this raises
so many questions.

SHATNER:
Based on the carvings
on the walls

and artifacts
recovered in the chambers,

archaeologists estimate

that the extraordinary
Longyou Caves

are roughly 2,000 years old.

While there are similar

ancient underground structures
throughout China,

the size and sophistication
of the Longyou Caves is unique.

But just who exactly
carved these enormous caverns,

and why, remains a mystery,

because there is no mention
of this site

in the historical record.

How is it possible
that the existence

of 24 caves can go unrecorded?

This is very strange
because the Chinese

have always been very meticulous

in the way that they’ve
recorded provincial data.

And yet,
there was absolutely nothing.

No mention whatsoever
of these caves.

CLEMENTS:
The caves themselves

are so massive,
such a huge undertaking,

it’s not something
that a bunch of local villagers

might have done for a hobby.

We can estimate that it
would have taken 1,000 people,

working 24 hours a day,

six years to carve out
these caverns.

There ought to be some kind
of geographical feature,

some kind of odd-looking hill

or an infield valley
or something,

where all that sandstone
has gone,

but we don’t know where that is.

SHATNER:
In recent years,

some historians have suggested
that the Longyou Caves

disappeared from history
because they were intended

to be secret caverns

that were never meant
to be found.

We do not know
who built the caves.

But we can guess,
considering the fact

that they’re 2,000 years old,

that they were built in a period
called the Warring States.

And at the time,
China was a patchwork

of different kingdoms
all fighting each other.

And the fact
that they are not mentioned

in ancient documents
could well be

a factor of their use for
some kind of strategic purpose.

So, "We’re not gonna
tell the enemy

"where our secret bunkers are.

We’re not gonna tell them
where our secret supplies are."

SHATNER:
Could the Longyou Caves
have been

a subterranean place
to hide critical supplies,

or even people,
from encroaching enemy forces?

Or could their purpose
be tied to the deep waters

that shrouded their location?

What’s interesting about
the Longyou Caves

is it seems
that when they flooded,

the water helped maintain
the structural integrity.

Somehow, it took the load off

some of the beams, for example,
holding up the roofs.

Now that the caves
have been drained,

the Chinese have been obliged
to add extra buttressing

to hold them up.

And so,

I think they were

a storage facility.

Um, and I think certainly many
of them were intended for water.

The area is drought prone.

So in the event of some kind
of military crisis,

it would have been very handy
to have a secret base

with enough water for them
to live on for years.

SHATNER:
Were the Longyou Caves hidden
beneath a pond for centuries

because they were built
to be a secret water reservoir?

Or could they have had
another purpose,

that has yet to be unearthed?

For now, the answer
remains lost to history.

But in modern times,
the caves have become

an important source of pride
for the people of Longyou,

who regularly hold festivals

in this ancient
underground space,

to commemorate their heritage.

The story
of the Longyou Caves is

actually very fascinating
because

it would seem that by looking
beneath the earth itself,

we’re obviously going
to discover many, many caverns,

underground chambers,
or even cities

done by human hands
that have been completely lost,

and that’s
a very exciting prospect.

Who could have built
the Longyou Caves?

It’s a question
that continues to baffle

both historians
and archaeologists alike.

And the discovery of this
massive underground complex

shows us just how easily
entire societies can vanish

from the pages of history.

But there is another
subterranean mystery,

where labyrinths
of bizarre tunnels are not

confined to one specific region
but instead are found

underneath an entire continent.

SHATNER:
In this quiet rural town,

a Bavarian dairy farmer
watches in horror

as one of her cows falls

into what appears to be
a sinkhole.

But after thankfully
rescuing the animal,

the farmer discovers

that her cow hadn’t
stumbled into a sinkhole

but rather a mysterious
subterranean ruin

known as an erdstall.

Erdstall are
human-carved tunnels

that extend into the ground.

You know, they’re,
they’re chiseled out of stone.

COLLINS:
They are like mini labyrinths,

mini underground cities,

and the erdstalls consisted

of a series
of chambers and tunnels

and stretched for about 125 feet

and was on different levels.

And archaeologists have
investigated it,

and have suggested
that there was activity there

as much as a thousand years ago.

SHATNER:
But this isn’t the only
erdstall that’s been discovered.

In fact,

similar man-made tunnels
have been found hidden

all across southeastern
Germany and Austria.

Many of them are found
just in the middle of nowhere,

um, you know, out in somebody’s
field or something like that.

Or within the cellar areas

or foundations of old houses,
old structures.

Some of them may be
very limited.

You go in and there’s just
sort of one little chamber

or two little
interconnected chambers.

And some of them
extend hundreds of feet

in many different
directions with,

you know, all sorts of different

little sort of
side chambers and passages.

COLLINS:
We don’t know who carved them.

We don’t know
when they were carved.

We don’t know
their original purpose.

Because of this,

the erdstall tunnels are
incredibly mysterious.

SHATNER:
One investigator driven to solve

the mystery of the erdstalls
is Dieter Ahlborn.

He has been exploring
these tunnels

for more than 20 years.

SHATNER:
To date, more than 1,200
long-abandoned erdstalls

have been found beneath
the German and Austrian soil.

But why would anyone go

to such lengths to carve

these bizarre underground
structures in the first place?

PAUL BAHN: The erdstall,
which basically means

earth stable or earth stall,

is a name given
to a whole series

of many hundreds
of small tunnels

that exist primarily
in Bavaria and Austria,

and which are one of the great
mysteries of the world,

even today.

They’ve not been known
for, for very long.

Normally, if you’ve got tunnels

or caves, you will find

bones or-or artifacts
or something inside them.

There is nothing

in these erdstall
and that has made it

very, very difficult to know
what they were for.

TREISTER:
They’re obviously
completely dark,

and, interestingly, you don’t
see areas where there were,

like, hearths or fires.

You don’t have,
you know, charcoal.

But there are also these
tiny little areas carved out

for a place where
like a lamp would be placed

so that people who are actually
building would be able to see.

So it’s clearly--
it was very well-planned

and designed
and executed, and yet,

we don’t know
what they were built for.

SHATNER:
If the erdstalls weren’t made

for any practical purpose,
then why were they built?

Well, some people believe
that they weren’t created

to be used
by the living but rather

they were designed to be
a resting place

for the souls of the dead.

A very unique theory,
uh, about erdstalls

was that there was
a lot of Christian ideas

as to their function.

And they would have been used

to collect
the souls of the dead...

...where they would remain
until the day of judgment

and then they would rise
to go to heaven.

SHATNER:
Is it possible

that the erdstalls were
constructed by Christians

throughout Central Europe

to be holding chambers
for people’s souls

as they waited
to get into heaven?

Perhaps.

But on the other hand,
there are some archaeologists

who believe that explanation
isn’t quite good enough.

And one reason is that--
as it turns out--

erdstalls aren’t only being
found in Germany and Austria.

People are discovering them
all over Europe.

BAHN: There are similar tunnels
in many parts of Europe.

Even Israel has some,
but it’s very, very difficult

to see any kind of linking,
uh, phenomenon between them.

Perhaps there was
some widespread belief

that we know nothing about

because they were clearly
of great importance.

TREISTER:
Humans have been able to chisel

into stone
for thousands of years.

There’s probably
countless structures

throughout the ancient world
that are in places

where we just don’t know
that they exist.

SHATNER:
Were the erdstall tunnels built
to hide from one’s enemies,

or to store
the souls of the dead?

The theories surrounding
these narrow winding passages

are as vast and varied
as the tunnels themselves.

But there’s another theory,
that pushes the idea

of not just
an underground society

but of an entire
underground world.

SHATNER:
Acclaimed novelist
Jules Verne publishes

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?

BRANDENBURG:
One of the most
fascinating people

in the history of science
is Edmond Halley,

who the Halley’s Comet
is named after.

Based on his explorations,

he discovered the Earth’s
magnetic field is 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.

REDFERN:
Edmond Halley believed there
were essentially three crusts,

three rotating crusts
which surrounded

this huge, hollowed-out portion
of planet Earth.

SHATNER:
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.

REDFERN:
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.

The primary reason
why Admiral Byrd

was able to go
on these expeditions

was because he was
a very adept pilot.

He was actually
given the Medal of Honor.

That demonstrates
as to how revered he was

in terms of his expeditions.

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.

NEWMAN:
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.

REDFERN:
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
a fully-grown woolly mammoth,

which-- it would be amazing
if that was true.

SHATNER:
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 is 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 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.

SHATNER:
How deep
will we eventually send humans

down into the mysterious depths
of our planet?

Even utilizing
advances in technology,

the journey through
the Earth itself is difficult.

What have recent
mining efforts revealed

about what lies below?

SHATNER:
In this nation,

located between South Africa
and Mozambique,

stands an ancient,
stepped mountain canyon

known as Bomvu Ridge.

The Bomvu Ridge is significant

because according to experts,

it is the site
of the oldest mine in history.

Radiocarbon dating, uh,
shows evidence

that this place was mined
40,000, 50,000 years ago.

And 50,000 years later,

the place
is still producing iron today.

So the history
of the human species,

from the Stone Age
to the Digital Age,

has this relationship
to going after

the metals that we need
at that particular place.

SHATNER:
It’s astonishing to think
that from the humble beginnings

of the first mine
at Bomvu Ridge,

there are now more
than 6,000 active mines

located all over the world.

Some of today’s mines extend
incredibly deep into the Earth,

such as the Mponeng Gold Mine
in South Africa,

which reaches an astonishing
2.5 miles underground.

The deepest gold mine
is located in South Africa.

It’s about four kilometers deep.

You have to do
a couple of different things

if you want to mine stuff
from that far underground.

It’s one thing
to drill a hole, right?

It’s another thing
to drill a hole in such a way

that you can send
people and equipment

safely there and back
on a daily basis.

You have to be on the lookout

for evidence
of minor fault lines, right?

The tiniest earthquake,
the tiniest shift

can be catastrophic when
you are mining at those depths.

SHATNER:
Every year, more than
3.2 billion tons

of iron, gold, silver, platinum
and other precious metals

are extracted from our planet.

Today, we rely on mining

perhaps even more
than our ancestors did

because modern electronics
depend

on what are referred
to as rare earth elements.

The term rare earths refer to
17 chemically similar elements

that have fantastic magnetic
and conductive properties.

They are called things
like europium, lanthanum,

praseodymium, cerium,
and together

they are absolutely essential
for life as we know it today.

We need these elements
for medical technologies,

communications,
computer hardware.

But eventually
rare earth elements

are going to peter out.

And the real question is,

how deep will we go
into the Earth

to get the elements
that we need?

I think the simple answer
to that is,

we will go as far as
our technologies allow us to go.

SHATNER:
Will the Earth’s supply of
rare metals eventually run out?

It appears the only way
to find out

is to keep digging
into our planet

in search of both
essential resources and also...

answers to the many mysteries

that lie beneath our feet.

EDWARD GARNERO:
As humans, we share

this curiosity,

this desire to understand
what’s beneath our feet.

And we want to explore.

We want to follow
the breadcrumbs of this mystery

of what is down there.

COLLINS:
Geophysical research
is revealing cave systems,

caverns,
and obviously whole cities

that were never
known about in the past.

And we are going to discover
incredible things

beneath the earth
in the future

that we could not even
have imagined existing before.

NEWMAN:
There are just so many
of these incredible

underground cities,
caverns, crystal caves,

tunnels and catacombs
everywhere around the planet.

It does feel like
we’ve just really

scratched the surface
of what could be below us.

There could be much more.

There’s a remarkable
amount of research

still to be done under
the surface of the Earth.

While it’s clear that there
are still many mysteries

right beneath
the Earth’s surface,

maybe the next time
a lake is drained,

the remnants of a lost
civilization will be uncovered.

Or perhaps the discovery
of an artifact

or ancient inscription
will explain

why our ancestors dug elaborate
tunnels deep underground.

What other
subterranean hiding places

are yet to be discovered?

What secrets do they hold?

Well, for now that remains...
unexplained.

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