Original subtitles

WILLIAM SHATNER: A vast subterranean chamber

hidden for centuries.

A legendary lost treasure buried in an ancient mine.

And a town in the Australian Outback

that is located entirely underground.

For as long as humans have walked the Earth's surface,

we've also wondered about

what lies beneath our feet deep underground.

Are there profound secrets about our planet

buried beneath layers of rock, or hidden in vast caves?

What can the subterranean world

tell us about humanity's past,

and perhaps even its future?

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

♪

SHATNER: Human beings have a strong desire to learn

everything we can about the planet that we live on.

After all, we've launched satellites into outer space

that have photographed every inch of the Earth's surface,

and we've used deep-sea submarines

to journey to the bottom of the ocean.

However, there is one final frontier in our world

that remains almost totally shrouded in mystery.

For we have yet to fully explore the vast underground depths

of our planet Earth.

It's really uncommon for someone to know how deep the Earth is.

Very smart people often guess, "hundreds of miles?"

When in fact, it's 4,000 miles to the center of the planet.

L.A. to New York is just a fraction of that,

with the 2,700 miles.

The mass of the Earth is great.

And when you think about the amount of rock

that's piled on rock, on rock,

that pressure is incredible and prevents us from going deeper.

So, what's beneath our feet?

We don't know.

Mankind's relationship with the underground

stems from our innate curiosity,

and the ground beneath our feet is open season for that.

SHATNER: Today, scientists and explorers are compelled

to investigate the subterranean world,

in hopes of shedding new light in the darkness of its depths.

But these efforts are just the latest chapter

in humanity's long quest to learn more

about all that we cannot see beneath us.

In fact, our fascination with the secrets of the underground

stretches back thousands of years.

Going back 3,500 years, we find drawings and paintings

underground where it's completely dark.

So, we can see how our early ancestors

connected mythology to the underground,

in terms of their relationship to the Earth.

These explorations and forays

meant something on a spiritual level.

They were pushing as far as they could go

with the technology that they had.

BRADLEY GARRETT: The underground has always been important

in human history, and it's tantalizing

but it's also kind of frightening.

For instance, we can look to Hades in Greek mythology,

this underworld which is a metaphor

for not being blessed by the light of the heavens.

Also, we can look to Dante

going into the seven circles of Hell in an Inferno.

All of these point to an underground space

that you'll go into and never come out from.

(man screaming)

SHATNER: While often described as a place of danger,

darkness and doom in the legends and folklore

of cultures around the world,

it was during the 18th and 19th century

that the perception of an underground world

became less mythological and more scientific.

This evolution in thinking is perhaps best illustrated

in author Jules Verne's seminal novel

Journey to the Center of the Earth,

which was published in 1864.

LYNNE McNEILL: Jules Verne's Journey to the Center of the Earth

is the story of a professor, his nephew and their guide

going into the center of the Earth

through a volcanic crater in Iceland...

...making their way through these subterranean passages

and finding prehistoric plant life

and creatures and maybe even a suggestion

of some sort of humanlike creature

that they glimpse but don't interact with.

Jules Verne was a well-read author,

he was up on the science of the day,

and he made a really scientific effort

at describing an entire subterranean world.

It's a fictional book,

but it really resonated with people's imaginations.

SHATNER: Journey to the Center of the Earth

had a profound effect not just on science fiction readers

but also on actual scientists,

who were inspired to explore deeper than ever before.

By the 20th century, modern drilling technology

gave scientists a new tool for satisfying

our ongoing curiosity about what lies underground.

The most famous effort to drill into the planet started in 1970,

when the Soviet Union embarked on an ambitious attempt

to reach as deep as possible into the Earth.

The project, which was conducted

on the Kola Peninsula in Russia, lasted for more than 20 years,

and resulted in what is referred to

as the Kola Superdeep Borehole.

The hole, which is nine inches wide,

reaches an astounding 7.6 miles into the Earth.

The Kola Superdeep Borehole

is just a really thin, narrow hole

straight down into the Earth.

One of the reasons why they made the hole that shape

is that the wider the space it is that you're drilling,

the more resistance that you run into.

One of the biggest obstacles

to digging that hole was the temperature increases

about 60 degrees Fahrenheit

for every kilometer that you go down.

These teams found, when they were drilling down,

that the rock started to behave like plastic.

And that the solid rock was actually gumming up

the works of-of their drills.

ROBERT SCHOCH: There's so much pressure there,

there's so much heat there, eventually,

they could drill no deeper and they had to abandon it.

And since then,

there has been no project that has gotten deeper.

It's actually the deepest hole that has ever been drilled

to this day by humans.

SHATNER: While the Kola Superdeep Borehole

is an inspiring feat of engineering,

at 7.6 miles in depth,

it only reaches less than one percent

down to the center of the Earth.

And in fact, many experts believe that instead

of using drills to dig into the underground,

we should instead listen

to subtle vibrations in the earth

that are called seismic waves.

By studying seismic waves,

scientists detected two giant structures

deep inside of the Earth's mantle.

These formations are so oddly shaped

that they are commonly referred to as "Earth blobs,"

and according to experts, Earth blobs pose a dire threat

to the survival of humanity.

GARNERO: These blobs are massive.

Hundreds of miles tall, the size of continents,

very irregular in shape, and they're very hot.

The temperature of the surface of the Sun

is the temperature of these things.

There's the possibility that over time,

these blobs might rise

and come to the surface and would result

in crazy intense volcanic eruptions.

MICHIO KAKU: The gigantic energy

from a volcano comes from underground,

underground from the core of the Earth itself,

creating a catastrophe beyond human comprehension.

And so, when it comes to what's underneath our feet,

we have to watch out.

It's staggering to think

that we've only managed to drill

less than one percent into the Earth's crust.

But even so, archaeologists continue to make

shocking underground discoveries all the time,

such as a baffling man-made cave system in China

that was carved thousands of years ago

by a mysterious unknown civilization.

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 the 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

a thousand 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.

Archaeologists are conducting ongoing excavations

in an attempt to unravel the mystery

of who built the incredible Longyou cave system.

But some experts believe the best way to solve

an underground mystery is not by digging,

but rather by researching historical texts.

For instance, there's a copper mine

in southern Israel that, according to the Bible,

may have been the hiding place of King Solomon's treasure.

SHATNER: In the deserts of southern Israel

lies a mountainous region that is called the Timna Valley.

Today, this area is known

for its uniquely shaped sandstone cliffs.

But more than 3,000 years ago, the Timna Valley was the site

of a vast network of copper mines.

MULLINS: In the Timna Valley, mining activity took place

for a long, long time,

and most of the mining operations

took place underground.

The deepest is about 115 feet.

They would hew in the ground circular shafts,

and going down that shaft,

they would cut steps into the side of the shaft.

And they would tunnel along horizontally,

where they would extract the copper

and take it back up to the surface.

SHATNER: In recent years, the Timna mines have attracted attention

because there are those who believe

that buried underground in one of these deep tunnels

is the legendary lost treasure of the biblical King Solomon.

In the Old Testament of the Bible,

King Solomon is described as a noble

and wise ruler of Israel.

Historians believe that Solomon was a real person

who lived in the 10th century BC.

King Solomon is an intriguing figure

because the Bible makes so many claims about him

controlling vast amounts of territory.

According to the Bible,

Solomon expanded ancient Israel considerably,

from the Euphrates river in the north

all the way to the River of Egypt,

and so, a much more expansive territory.

The Bible also describes

Solomon controlling vast amounts of wealth.

Solomon decides to build a temple, uh, in Jerusalem.

The temple becomes the home of God,

and he spares no expense.

And he was so committed

to having the best temple in the region

that he actually imports the finest materials

to build this temple.

SHATNER: According to the Bible, Solomon's temple was built

from the best limestone and cedarwood.

Inside, the walls were overlaid with pure gold,

and Solomon adorned the temple with objects made out of copper,

which was also a precious metal at the time.

King Solomon ruled Israel for 40 years

before dying in 931 BC.

Upon his death, Solomon reportedly left behind

an enormous amount of gold and other riches

in his magnificent temple.

But then, in 586 BC,

the Babylonians invaded Jerusalem

and sacked Solomon's temple.

When the Temple of Solomon was destroyed in 586 BCE,

all the temple treasures were lost to history.

An ancient legend says that Solomon's treasures

were taken out of Jerusalem and buried.

There are those who believe that the treasures

are, to this day, still hidden.

SHATNER: For centuries, the legend of King Solomon's lost treasure

has been a source of fascination and mystery.

In 1885, the story was exposed to a wider audience

when author H. R. Haggard wrote his famous novel

King Solomon's Mines,

which speculated that Solomon's treasures

were hidden deep in an underground mine shaft.

But if there is some truth to this legend,

then where is King Solomon's treasure buried?

For some, the most likely location is the Timna mines.

MULLINS: The Timna Valley is located

not more than 150 miles from Jerusalem.

So we're talking about close proximity.

At Timna, there are 10,000 mine shafts, maybe more,

and so, it's easy for people to kind of say,

"There must be a connection."

SHATNER: In the last several decades,

numerous researchers have tried to prove that the Timna mines

are, in fact, the hiding place

of King Solomon's lost treasures.

Some of the first evidence in support of this theory

was found by an archaeologist named Nelson Glueck,

who conducted a series of excavations at Timna

in the 1930s.

COLLINS: Nelson Glueck

made a huge study of the-the copper mines,

the smelting works,

and also, the camps of those that were there.

And what he found under the ground was pottery

dating from the 9th to 10th century BC.

And this was the exact time frame

of the reign of King Solomon.

And so, for Nelson Glueck,

he felt that he had discovered evidence of Solomon's mines.

SHATNER: Nelson Glueck's discoveries

made sensational headlines around the world.

However, despite years of searching,

Glueck was unable to locate the fabled treasure,

and some experts began to think that Glueck was wrong

to associate the Timna mines with King Solomon.

But then, in 2019,

a team of archaeologists led by Professor Erez Ben-Yosef

of Tel Aviv University, made a remarkable discovery.

While excavating an ancient mining worksite at Timna

that is referred to as Slaves' Hill,

they found more evidence that links this location

to King Solomon.

When you take the totality of this,

the Bible and what it says about King Solomon,

the presence of these copper mines in the deserts of Israel,

and put all these elements together,

for people of faith,

it gives them a greater assurance

of the truthfulness of the Bible,

that it involves real people

in real places in a real time.

Is the treasure of King Solomon

hidden somewhere in the Timna copper mines?

Experts continue to search for clues deep underground

in hopes of answering that long-standing question.

Not unlike another subterranean mystery

that has also persisted for centuries.

One that involves the strange theory

that there are vast open spaces

located in the center of the Earth.

SHATNER: Seismologist Dr. Paul Richards

and his team at Columbia University

make a remarkable announcement.

They discovered that while a full rotation

of the Earth's surface takes 24 hours,

the iron core at the center of our planet

actually spins faster.

AGNEW: They were measuring

the rotation of the core of the Earth

in relation to the surface of the Earth,

and what they found was that it's not constant.

And it leads people to believe

that there is a disconnection between the two.

Maybe it's not molten rock.

It could be open air.

So, when you put all of that data together,

it leaves open the idea,

the hypothesis, that Earth is hollow.

Could there really be vast hollow space

beneath the Earth's surface?

It sounds crazy.

And yet, for thousands of years,

the belief has persisted that beneath our feet

there are not just caves and tunnels

but an entire underground world.

The idea of the Hollow Earth is that we live on a shell

and that inside the Earth is a hollow cavity

with its own atmosphere, its own animals,

and possibly, its own inhabitants.

AGNEW: The concept of a Hollow Earth

goes well back before written word.

We have pictograms,

cave drawings, things that describe

either deities coming out of the Earth

or man trying to communicate with deities in the Earth,

and that's where the idea of a Hollow Earth came from.

SHATNER: Of all the ancient tales about Hollow Earth,

perhaps the most intriguing

is one that involves the Garden of Eden.

TZADOK: There is an ancient legend

that is recorded from a very, very old text

called the Sefer HaTemunah, the "Book of the Image."

The legend tells us

that a cave called Machpelah

is the doorway to the Garden of Eden...

...which exists in inner Earth.

But here's the interesting question:

a garden in a cave?

It doesn't work like that.

Gardens have plant life that grows, requires sun.

But in inner Earth, there's an inner sun.

SHATNER: Could Adam and Eve have lived

in a lush paradise deep underground?

The incredible notion that people

could inhabit subterranean spaces

has been embraced not just in ancient times

but also, in the modern era.

In fact, by the turn of the 20th century,

the fascination with Hollow Earth was so strong

that a new generation of scientists and explorers

set out to find proof of the existence

of a so-called "Inner Earth."

Perhaps the most fascinating of those expeditions

was led by an American Naval officer

named Admiral Richard E. Byrd in 1926.

Admiral Richard Byrd

was a famous American aviator and explorer.

And he claimed that on one of the journeys

that he made to the North Pole--

in an aircraft-- he came across

an environment down below that was plush and green

with animals, almost like a sort of Garden of Eden, if you like.

In other words, what was seen, perhaps, by Admiral Byrd

at the North Pole was actually an entrance

into a parallel world,

a parallel existence

that exists and coexists with the Earth itself.

SHATNER: Is it possible that Admiral Byrd

saw an entrance to Inner Earth at the North Pole?

Almost a century after his alleged discovery,

there's no way to know for sure.

But modern science is trying to solve

this centuries-old mystery by conducting seismic studies

of the interior of the planet.

One of the pieces of data that was really earthshaking

was when Washington University published the discovery

of another ocean underneath the crust of the Atlantic Ocean.

They could actually read the waves crashing on a shore

on the inside of the crust.

That was really quite remarkable.

When I see reports like that, it leads me to believe,

at least, that there's a possibility

that we have a Hollow Earth.

If we gather evidence to prove

that our planet is actually hollow,

it could change everything.

Maybe the ancients were right all along.

Does the Earth really have enormous hollow expanses

beneath its surface? (chuckles)

It's a wild thought to consider, but one way or another,

we may soon find out the answer.

Because according to some, the future of humanity lies

not on the surface of the planet

but rather deep underground.

SHATNER: On the surface, this remote town

which is located in a harsh sandstone desert,

looks like a normal rural community.

But appearances can be deceiving,

because as it turns out,

most of the town is located underground.

Beneath the surface of Coober Pedy

lies a subterranean world,

complete with homes that are known as "dugouts"

and other living necessities.

Coober Pedy is-is an incredible town in the Australian Outback.

You go down these ramps into an underground space,

and then, you start seeing restaurants,

hotels,

people's houses,

churches underground.

All of this stuff excavated from this soft but very firm rock.

SHATNER: What would possess people

to live in such an unusual, underground community?

Well, the history of subterranean living

in Coober Pedy dates back to 1915,

when miners first traveled to this area

to dig for gold and precious opals.

GARRETT: The name for Coober Pedy comes from Aboriginal people

that lived there when the first explorers came out.

Coober Pedy means "white man in a hole."

(laughs) 'Cause they saw these people

digging into these things and disappearing into the Earth.

And of course, were confounded, like,

"Why do you keep going in there?

What do you want in this place?"

(machinery whirring)

SHATNER: Today, Coober Pedy is more famous

for being an alternative lifestyle community

than it is for opal mining.

According to recent estimates,

there are 1,000 individual dugouts carved

into the rock at Coober Pedy,

and approximately 2,500 people

live and work here year-round.

SHATNER: But do residents of this unorthodox community

enjoy their subterranean existence?

Well, if you ask the people of Coober Pedy,

they'll tell you they wouldn't want to live any other way.

SHATNER: While the story of Coober Pedy

and its residents is extraordinary,

some people believe that underground living

is not a matter of lifestyle preference

but rather, survival.

In recent years, an increasing number

of so-called "doomsday bunkers" have been built,

which are designed to protect residents

in the event of a catastrophe.

One of the most prominent of these subterranean shelters

is Vivos xPoint,

which is located in South Dakota.

Vivos xPoint is the largest survival community on Earth.

It was originally a government facility

that was in charge of munitions for World War II.

We have 575 bunkers

spread out across 7,000 acres,

or about nine square miles,

which is about half the size of Manhattan,

that are now being used for underground living and survival

in case of the worst possible events we might encounter.

People who live out there,

they're regular people like you and I.

And they come from all different walks of life.

I think it always pays to be prepared

to survive whatever may come.

GARRETT: If we think about

bunkers that are being built around the world,

all of these spaces are connected

by a fundamental belief

that the underground is a space of protection.

So it completely makes sense,

because humanity has always sought the underground

to hide from a hostile environment.

In the future, will millions of people

actually live a subterranean existence?

It may seem unlikely,

but the truth is that humanity's fate

may indeed rely on what's deep underground.

For instance, there are places where people have drilled

two and a half miles beneath the surface of the Earth

in search of a rare and precious metal

that is critical to our survival.

Gold.

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, 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

two and a half miles underground.

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.

KLINGER: The term "rare earths"

refers 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.

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.

There is something that compels humanity to explore underground,

whether we're looking for precious metals

or building new living spaces

or simply satisfying our desire to descend into the unknown.

And just like our ancestors before us,

we'll keep digging in search of all the subterranean secrets

held by our planet that, for now, remain...

...unexplained.

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