Original subtitles

NARRATOR: A temple of the dead in the Yucatan,

an underground city in Turkey, and a South American cave

said to contain a treasure from beyond the stars.

For centuries people have told tales of caves and tunnels

deep inside the Earth, subterranean passageways

that lead to lands of gods and monsters.

But is there a surprising truth behind these legends?

-I have stood in front of drawings on the rocks

and wondered, am I looking at the extraterrestrial biological

entity?

NARRATOR: Could there really be mysterious places

far beneath our feet, places whose origins might not

be of this Earth?

-There were certain aspects of the caves, for which geology

could not provide an answer.

NARRATOR: Millions of people around the world

believe we've been visited in the past

by extraterrestrial beings.

What if it were true?

Did ancient aliens really help to shape our history?

And if so should we be looking for proof of their existence,

not in the heavens above, but in mysterious worlds

deep beneath the surface?

[MUSIC PLAYING]

[HOWLING]

-Bordered on the north by the Black Sea

and by the Taurus Mountains to the south

lies Cappadocia in central Turkey.

Here wind and water have sculpted strange shapes

out of the soft volcanic rock, rock which ancient peoples once

turned into small primitive dwellings.

In more recent years the site has

seen the construction of more modern structures.

But in 1963 a simple home renovation

in the town of Derinkuyu led to an extraordinary discovery

when a cave wall was opened revealing

a passageway to an underground city thousands of years old,

and more than 280 feet deep.

GIORGIO TSOUKALOS: I've been there on multiple occasions,

and it's incredible because there's

13 stories that go deep into the ground with ventilation shafts

and 15,000 little shafts that bring air

to even the deepest of levels.

NARRATOR: Incredibly the number of rock rooms that were found

could hold over 20,000 men, women, and children.

There was even evidence of religious centers, store rooms,

wine presses, and stables for livestock.

JOHN BRANDENBURG: Oh, Derinkuyu would

have been a massive undertaking for anyone,

even in modern times with modern equipment, but in those days

it would've been stupendous, equal to the pyramids.

At Derinkuyu because of the softness of the stone

you had to be very careful that you provided enough pillar

strength to support the floors above,

otherwise you'd have catastrophic cave-ins.

Surprisingly there's no evidence of any catastrophic cave

in, so they were apparently extremely clever

and knew their material.

We're talking deep antiquity.

It is mind boggling to understand

how they could have done this.

Perhaps they had help from some other civilization.

NARRATOR: But just who built this massive underground city?

And what mysterious force drove them to live underground?

DAVID CHILDRESS: Why would people

want to live deep underground in these weird caverns like that?

It seems kind of scary really.

NARRATOR: According to many archaeologists and scholars

Derinkuyu was most likely intended

to serve as a temporary shelter from invasion,

built around 800 BC by the Phrygians,

a Bronze Age people related to the Trojans.

Others believe it was built by the Hittites,

a warrior people mentioned in the Bible

who flourished hundreds of years earlier.

But could the underground city be even older?

According to ancient astronaut theorists

it is, perhaps by many thousands of years.

DAVID WILCOCK: The Cappadocia region of Turkey

was part of the Zoroastrian Empire, which

was Persian in nature, and it's one

of the oldest religious traditions

on the face of the earth.

NARRATOR: The Zoroastrian religion, an ancient faith

based on opposing forces of good and evil,

is widely believed to have influenced

both Hinduism and Judeo Christianity.

Founded sometime before the sixth century BC its chief God

is the creator, Ahuru Mazda.

And in the second chapter of the Zoroastrian sacred text,

the Vendidad Ahuru Mazda saves mankind

from a worldwide environmental disaster,

much like the story of Noah in the Hebrew testament.

GIORGIO TSOUKALOS: The great prophet Yema

he was instructed to build a kind of underground refuge

similar to Derinkuyu by the sky god Ahuru Mazda.

NARRATOR: According to the sacred texts

Yema built a multi-level underground city

to protect a select group of people and animals,

not from a flood, but from a global ice age.

The Vendidad calls this the evil winters.

According to many mainstream climatologists

the last ice age peaked around 18,000 years ago

and ended around 10,000 BCE.

Is it possible that Derinkuyu was

built as a refuge from a devastating global winter?

GIORGIO TSOUKALOS: Since you cannot carbon date stone

it's anybody's guess how old Derinkuyu really is.

And my question is, if we have a Zoroastrian story that's

very similar, could it be that both that place and Derinkuyu

are much, much older than what we've believed so far?

NARRATOR: But if Derinkuyu is, in fact, the underground city

that Ahuru Mazda told his followers to build

could there be a stunning truth behind the legend?

If so who or what was the god Ahuru Mazda?

DAVID WILCOCK: Ahuru Mazda does appear

to be responsible for the management of whatever

is happening here on Earth.

There are various ways to read this.

One of which is that it does represent some sort

of higher, universal form of consciousness,

but another is that it would represent

an overseeing extraterrestrial intelligence.

JASON MARTELL: Several sacred texts from antiquity

speak of knowledge given to mankind from extraterrestrials,

but also known as gods from antiquity.

NARRATOR: Could the sky god Ahuru Mazda really

have been an advanced being from another world?

If so, did he provide the technology

needed for his followers to build this complex labyrinth

as protection from environmental disaster?

Or is there possibly a more ominous reason

for Derinkuyu's existence?

Some say a clue lies in the underground city's

unusual security system, 1,000 pound doors on rollers that

allow them to be moved by a single person,

but only from one side.

JOHN BRANDENBURG: The Derinkuyu doors

are very cleverly constructed.

You can basically only open it and leverage it

from the inside.

GIORGIO TSOUKALOS: So obviously whoever inhabited Derinkuyu

was hiding from someone or something.

NARRATOR: According to the ancient Zoroastrian texts

Ahuru Mazda soared through the sky in a divine chariot

and waged war against his eternal enemy,

Angra Mainyu, the demon of destruction.

But could this really be, as many ancient astronaut

theorists believe, a depiction of two extraterrestrial forces

battling over control of the Earth and its resources?

GIORGIO TSOUKALOS: The aerial enemies were extraterrestrials

because they were the ones who had the capability of flight.

They had access to those types of machines

that we can read about in every single ancient culture

around the world.

DAVID WILCOCK: When you look at the Zoroastrian tradition

you also see clear evidence that there

was some kind of extraterrestrial battle going

on between warring factions.

Therefore it is certainly possible

that the original caves may have been

used as shelters against possible aerial bombardment

from extraterrestrials that were warring with each other

during that time.

-Derinkuyu was built out of fear of an aerial enemy.

Because if something flies over you very, very fast

you can't see the ventilation shafts.

Some suggest 30,000 people used to live underground

at Derinkuyu.

NARRATOR: During recorded history

many different peoples did, in fact,

hide in the underground city of Derinkuyu

to escape everything from desert raiders to Roman legions.

But some experts wonder whether such conventional attacks

can really explain why Derinkuyu was built in the first place.

GIORGIO TSOUKALOS: If it were an enemy that was on horseback

it would be easy for them to just smother everyone inside

by just closing all the ventilation shafts.

JOHN BRANDENBURG: We had the phrase in the defense

department studies that I've participated

in that the cave is a grave to a well prepared adversary.

Once you find it, it is highly vulnerable.

NARRATOR: But did the people of Derinkuyu

really go underground to avoid becoming casualties

in an extraterrestrial battle in the skies?

And if so, might there be other such cities

from the distant past?

According to ancient astronaut theorists

there are, and they can be found much nearer to home,

deep in the caves of the American Southwest.

NARRATOR: The majestic mesas and rugged mountains

of the American Southwest are home

to many native peoples including the Navajo, Zuni, Pueblo,

Hopi, and Apache.

These tribes have many different believe,

but their creation myths all share

something quite remarkable.

-Where we're talking about our origin, and you know,

you hear the stories about us coming down from Alaska

through the Bering Strait, but what we believe

is we came out from the ground.

DAVID CHILDRESS: The Apaches and other Pueblo Indians,

such as the Zunis and the Hopi Indians,

all have this legend that they emerged

from some underground world into today's world.

NARRATOR: In some legends the southwestern peoples

went back underground for safety.

The Hopi of Arizona say their ancestors

escaped a deadly storm of falling stars with the help

of the snake people who took them

to shelters deep in the Earth.

Another Hopi legend speaks of the ant people

who protected them from storms of fire and ice.

DAVID CHILDRESS: The Hopi Indians survived cataclysms

by living in this underground world with the ant people

for a certain period of time.

And then eventually they emerged from the underground world

back into the surface world.

NARRATOR: Ant people.

Snake people.

Could these stories be based on ancestral tales of people

actually living underground, possibly

during the last ice age?

Or could the ancestors of today's southwestern tribes

have taken refuge in subsurface dwellings

similar to the underground city of Derinkuyu in Turkey?

If so, over the centuries might they

have developed physical traits like large eyes and fingers

that made them more closely resemble

actual earth-dwelling creatures?

-The shamans and the elders of Native Americans,

they will tell you that before these people were

able to emerge out of planet Earth

they were brought here by the star people, the star

gods, which arrived from outer space.

-I have stood in front of what are called the ant

people in some of the very strange, large eye drawings

on the rocks and wondered, am I looking

at Native American interpretation

of what today is called a extraterrestrial biological

entity?

GIORGIO TSOUKALOS: If extraterrestrials were here

in the remote past, there are multiple species out there,

is it possible that they might have

a looked lizard like and ant like?

And the answer is yes.

NARRATOR: Is it possible that these underground creatures

of Native American legend were actually alien visitors?

If so, could some of them still be

living beneath the surface of the southwestern desert?

For decades stories of encounters

with UFO's and alien beings have been

told among the people of New Mexico's Jicarilla Apache

Reservation.

Some of the aliens in these stories

bare a strange resemblance to the ancient tales of the ant

like and snake like beings from the Hopi legends.

-There is things up there that no one can explain.

NARRATOR: The Jicarilla Apache Reservation

is located next to the small town of Dulce, nestled

in the shadow of the over 9,000 foot high Archuleta Mesa.

DAVID CHILDRESS: It is from this mesa and mountain

that people claim they have seen UFO's flying out

of the mountain.

-It was a spaceship we saw right there,

and it was big, like maybe the size of a football field.

And then we seen this dome on top that was all glassed in.

And then my husband was looking at it with the binoculars,

and he saw two small people.

Well, we don't know what it is.

If we stayed here and they came down

I don't know what they would have done to us.

NARRATOR: Could the native tales of spaceships

and strange creatures be true?

Some UFO researchers and conspiracy theorists

believe that these eyewitness accounts are not only true

but are evidence of a secret collaboration

between underground aliens and the US military.

-The amount of military traffic over Dulce,

the unmarked helicopters, the black helicopters,

the heavy duty Chinooks, all these helicopter

spend a lot more time in Dulce than they

should if nothing were going on here.

Among the stories that we've heard from the Jicarilla

Apache is that they discovered vents,

actually right here on the mesa.

-A while back, when my brother was still alive,

we used to come up here in the back,

and he showed us the shaft, and that thing

was bigger than, bigger than me.

But we walked in, and I didn't want to go any further.

BILL BURNES: The vents were here maybe 25 years ago.

You'd hear strange noises, groins, sighs, human groans,

and this led a lot of credence to stories

that human beings were being vivisected, experimented on.

And thus the legend of strange creatures

and strange noises coming out of this Mesa grew and expanded

NARRATOR: Aliens living underground, strange secret

government cover-ups.

Could Native American legends of underground beings

help unearth the truth behind these incredible stories.

Some think the answer might be found deep

beneath the surface of North America,

but others believe the truth lies

hidden in a mysterious cave thousands of miles

to the south, a cave that hides proof of alien visitors

who journeyed beyond the stars.

NARRATOR: South America.

The Andes mountain range in Ecuador.

For thousands of years this rain forest,

high on the eastern slopes, has been

the land of the Shuar, headhunters who are fiercely

protective of their homeland and it secrets.

And of all the Shuar's secrets, perhaps none

has been so carefully guarded as the location

and entrance of the cave of Tayos.

But why?

Perhaps the answer can be found in the story

of an Italian Catholic missionary, named

Father Crespi, who lived in the region

in the middle of the last century.

-Father Paolo Carlo Crespi.

He was loved by the Indians.

He helped them without asking for money,

and the Indians make them some presents.

NARRATOR: But what was unique about the presents

or gifts given to Father Crespi was that they often

took the form of elaborately carved artifacts,

some made of gold or other precious metals.

Often these objects featured elaborate carvings and symbols

not known to be associated with the Shuar culture.

In his 1973 book, "Gold of the Gods",

ancient astronaut theorist, Erich von Daniken,

wrote of father Crespi's incredible collection,

which he believed to come from the cave of Tayos,

and which were, in his opinion, treasures

from an unknown and highly advanced culture.

The startling questions posed in Von Daniken's book

soon inspired Scottish explorer Stanley Hall

to try and solve the mystery himself.

In 1975 Hall traveled to Cuenca to see Father Crespi's

collection with his own eyes.

STANLEY HALL: I had for years been researching South America

as the missing page of prehistory.

I first heard of the Tayos caves was in Erich von Daniken's

book, and followed it through from there.

-And one of the presents which the old priest received

is a tablet with certain six writings.

It's metallic tablet.

Know one alive today was able to translate these writings.

NARRATOR: In 1976 Stanley Hall mounted an expedition

of more than 100 people to explore Tayos.

Among them was American astronaut Neil Armstrong,

the first man to walk on the moon.

Entering the cave through a jungle entrance known

to the Ecuadorian army the explorers

were fascinated by what they encountered,

especially large areas that appeared

to have been excavated by someone or some thing.

STANLEY HALL: Head of the geological group, Brian Kelley,

in 1976 he admitted it was difficult

for him to explain the actual large doorways

that you see in these caves.

NARRATOR: Although Stan Hall's expedition did

find a tomb chamber with items dating to 1,500 BC

-A ring.

A stone ring!

NARRATOR: The expedition found no treasure,

and no trace of anything that looked like the artifacts

in Father Crespi's collection.

But if Tayos was not the secret origin of Father Crespi's

amazing collection, where did it come from?

Undaunted Hall didn't give up his search.

15 years later, in 1991, the explorer

tracked down an Ecuadorian named Petronio Jaramillo who

claimed to have entered the cave of Tayos

through a secret entrance back in 1946.

STANLEY HALL: And apparently Petronio

had visited this cave for the very first time when

he was very young, when he was in his teens.

He said that he had to dive under water,

go in this underwater tunnel and then come up.

NARRATOR: Jaramillo told Hall he wandered through chamber

after chamber of ancient relics, including a vast room of books

made from gold and other metals, books

with unrecognizable writing.

Possibly like that on one of the middle tablets

in Father Crespi's collection.

STANLEY HALL: Said other things looked like formulas,

and so on, and so on.

So it was one spectacular statement after another.

PHILIP COPPENS: Some argue to whether or not

an ancient civilization had come down to Earth

and had used this cave system to leave

certain artifacts of their civilization behind for us

to recover.

NARRATOR: Unfortunately, before he

could guide Stanley Hall to the underwater cave entrance,

Petronio Jaramillo died, taking the secret to his grave.

Stanley Hall himself died in 2008,

before he was able to renew its search for the so-called metal

library.

Fortunately, Stanley Hall's daughter, Eileen,

has decided to continue here father's work.

-Unless we find this treasure, unless we can see,

translate the writing it's still a big question mark

over who wrote it, why they put it there, and who put it there.

NARRATOR: But when Eileen Hall began

to look for the location of Father Crespi's

original artifacts she learned that much of the priest's

collection had mysteriously vanished shortly

after his death in 1982.

But why?

Had Crespi's artifacts fallen prey to thieves?

Or might the Shuar have taken the treasure back

into the cave where they found it?

Whatever the answer, Eileen Hall has

continued to research other artifacts from elsewhere

in Ecuador, and like father Crespi's objects,

some seem to have uncanny resemblances to other cultures

that according to mainstream archaeology

ancient Ecuadorians could not have had any knowledge of.

EILEEN HALL: This collection is made up

of what my father believed to be the formative cultures

of Ecuador.

This is from the coastal culture from 600 BC to 1600 AD,

and this is very human like, but at the same time

some features have been exaggerated.

Here you've got the smaller face with the kind of bigger ears,

and the elongated skull shape in the head.

-The top of this head looks like an elongated cranium,

an elongated skull, and it is identical

to this Egyptian statue that we find all over Egypt.

To see this picture right here and compare it

to the Egyptian bust we see right here, it's uncanny.

The head shape is identical.

NARRATOR: Do Stanley Hall's artifacts show evidence

that Egyptian culture could have crossed the ocean

to influence South American culture?

Or is it possible that both were influenced

by another culture, one from beyond our world?

If so were the strange writings inscribed on Father Crespi's

metal tablets actual messages from an alien world?

-My father went as far as saying it was possibly

an advanced civilization, but we can't know for certain

until this library is found.

-So this metallic library is still there, in Ecuador,

in a subterranean cave.

There are still Indian tribes living there.

They are still protecting the old treasure.

PHILIP COPPENS: So it's going to push the boundaries of academia

once this cave system has been found.

And whether it is Inca or extraterrestrial

it doesn't really matter at this moment in time.

Let's get to this cave and see what is in there.

NARRATOR: Perhaps Tayos has yet to reveal all of its secrets,

but more than 700 miles to the north

there is another cave, one that may

prove that the Mayan underworld and the terrifying gods who

ruled it were not only very real,

but thirsty for human blood.

NARRATOR: The Yucatan Peninsula, one of Mexico's premier tourist

destinations.

Besides scenic beaches, the area is

covered by thick jungle and pot marked

by massive sinkholes known as cenotes.

The ground beneath the jungle is also honeycombed with caves.

But here, in 2007, Mexican archaeologist Guillermo de Anda

found a cave like no other.

Following clues in the records of 17th century

Spanish priests that hinted at the existence

of a mysterious underground Mayan temple

deep in the jungle De Anda found a series

of caves near the village of Tahtzibichen.

Caves not seen for hundreds of years, and with entrances

submerged beneath centuries of flood water.

GUILLERMO DE ANDA: Sometimes we have to dive into these caves.

Sometimes they go very deep.

The average of our research is about 140, 150 feet,

but we know of caves much deeper than that.

NARRATOR: At first De Anda and his team

found carved stone heads and broken pillars

with 1900-year-old Mayan inscriptions.

GUILLERMO DE ANDA: We have found columns under the water.

And these columns are amazing because some of them

are five feet high and at least 10 feet wide.

NARRATOR: But as De Anda surfaced

in the dry areas of the cave he found what he believed

to be the remains of a massive underground temple complex,

including a concrete road, a crumbled pyramid, and bones.

But why was it here?

DAVID CHILDRESS: The Mayans themselves

have a very intriguing legends of an underground world called

Xibalba.

And it's believed now by archaeologists

that what they found is what the Mayans thought.

was the entrance to this legendary underground world

that features prominently in Popol Vuh.

NARRATOR: Could this dark and mysterious cave really

be the underground world mentioned in the Mayan legends?

According to the Popol Vuh, the written record

of Mayan mythology, the underworld kingdom of Xibalba,

meaning the place of fear, was ruled

by the cruel lords of the dead, who

made those who entered their realm

pass through a series of torture chambers

involving blood, darkness, cold, knives, bats, and jaguars.

JASON MARTELL: We see here in this one archaeological spot

an actual physical representation

of what the Mayans felt the soul had to go through.

NARRATOR: Might perhaps this cave of stalactites

sharp enough to pierce flesh represent

the room of knives in the Popol Vuh?

There is also a room of bats, and a trench that might once

have been filled with blood, like the river of blood

that Mayan pilgrims had to cross over.

There are places of cold and darkness,

and even a room with the bones of jaguars.

JASON MARTELL: These

with large patches of spiders and reptiles,

and all types of tumultuous things

that a human really wouldn't want to be exposed to.

Although some archaeologists claim

this unique site was simply modeled

after the description of Xibalba in the Popol Vuh,

De And insists that items from the cave

date back to a time centuries before the Mayan holy book

was written.

-It's not that there was this document

and they try to imitate what the document said.

I think it's all the other way around.

We believe that we have found the particular ship

above the central parts of Yucatan.

This is why we do believe it was a real place.

NARRATOR: But if Xibalba is real,

were the lords of the dead also real,

and if so, who or what were they?

-According to the Chilam Bala book,

which is the book of the Jaguar priests,

it says in there that at that time the road to the stars

descended from the sky and the 13 and nine gods came to Earth.

I'm sorry, road to the stars descended from the sky--

can it be more clear?

I don't think so.

Right there we have a direct reference to someone

that has arrived from outer space,

and we have a written record about this.

NARRATOR: Could the lords of Xibalba

and other Mayan gods really have been

extraterrestrial travelers?

If so, why did they display such a thirst for blood and torture?

DAVID WILCOCK: While I do not believe human sacrifice was

originally taught by the ET's I believe

it came in the aftermath of when the original teachers

of humankind had arrived.

The ancient gods, which were really

just humans from another world, withdrew from the area,

and the people became distraught.

The more they became distraught, the more

they took the original mythology and interpreted it

in a much more literal way.

So what might have started out as the myth about the sun

dying and being reborn when it sinks below the horizon

becomes literally the idea of killing people

to make sure that the sun is going to come back up.

NARRATOR: As archaeologists and explorers

continue to uncover sites where legend and reality meet

could there be even more evidence that mankind's

history on this planet is much more profound than what

we currently understand?

There are those who believe the secret lies even deeper

within the Earth, as deep as its very core.

NARRATOR: The North Pole, a seemingly endless wasteland

of Arctic ice, shrouded in darkness

for six months of every year.

Here there is no food, no shelter,

not even a cave to hide from the slashing

winds, and temperatures that can dive to 90 degrees below zero.

But according to mainstream geology

beneath the poll and the Arctic Ocean

lies the Earth's mostly rocky crust, up to 30 miles thick.

Below this is molten rock, heated by the planet's

spinning core, with a solid center of iron

and nickel the size of the moon.

Scientists have deduced this information

from measurements of Earth's gravity, magnetism,

and seismic waves.

But no one has ever seen these areas.

Could the frozen surface of the pole

be hiding a gateway to a world within our surface world?

There are those who believe the answer is yes.

And what they believe is known as the Hollow Earth theory.

-The Hollow Earth theory is that this Earth is not molten

inside.

It is actually hollow, and that suspended

in the hollow of the Earth is an inner sun.

NARRATOR: Surprisingly the notion of a hollow earth

was first given scientific credence

by one of the founders of modern astronomy.

DAVID STANDISH: The idea that the Earth might be hollow,

as a scientific notion, dates back to the astronomer

Edmund Haley, who was best known for his comet.

In 1691 he presented to the London Royal Society

his hypothesis that the Earth is hollow, and contains

several little spheres inside, sort

of like those Russian Matryoshka dolls.

He was hypothesizing this for a very practical reason.

The Earth's magnetic pole moved a little bit every year

to the west.

And his idea was that our outer sphere had inner spheres turned

independently of the outer one.

He also suggested that these interior spheres would also

be able to support life.

In 1818 former US Army Captain John Cleves Symmes Jr.

Announced that there were vast openings at each pole where

we could enter inner earth.

-With Symmes the idea of a hollow Earth

gets tied into exploring for the pole.

At this point nobody had actually

seen Antarctica, for instance.

NARRATOR: The Hollow Earth theory

again captured the public's imagination in 1864

with the release of Jules Verne's second novel,

"A Journey to the Center of the Earth".

DAVID STANDISH: The novel takes an Icelandic guide,

and a professor, and a young man down

into the center of the Earth.

"Journey to the Center of the Earth"

could really have been called a journey

to the center of geology.

Geology and paleontology were a very hot topic

in the early 1860's and there is a lot

of discussion of that in "Journey

to the Center of the Earth."

NARRATOR: But while Verne popularized the idea

that extinct life forms might still exist inside the Earth,

others envisioned that the Earth contained

advanced underground civilizations.

DAVID CHILDRESS: Supposedly they have advanced technology.

They've got ray guns, and special weapons,

and even they have flying saucers,

and other craft like that.

NARRATOR: But is there any evidence that such fantastic

claims could be true, and has anyone

actually been to the world within our Earth?

Proponents of the Hollow Earth theory say yes,

and that one the explorers was no less

a luminary than famed polar pioneer Admiral Richard E.

Byrd.

In the 1920's Byrd made world headlines

by flying over the North Pole and by becoming the first man

to fly solo over the South pole.

But Hollow Earth theorists believe

that the famous explorer went even farther,

and that on February 19, 1947 Admiral Byrd piloted a plane

through a hole near the North Pole

into the interior of the Earth.

ROONEY CLUFF: Flying saucer type craft

took control of his airplane with some kind of tractor beam.

And they landed him near an inner Earth city,

and the message that they had for us was that they consider

themselves the guardians of this planet.

OK?

He says, we don't approve of you people using nuclear weapons.

We had just blown up a couple of cities

in Japan a couple of years before.

So this was the message that he was given,

but when he got to Washington, they put a lid of secrecy

on this that this was not to go out.

NARRATOR: Some say Admiral Byrd's own account

of this flight into the hollow earth

is detailed in his secret diary, published in the 1990's, almost

four decades after his death.

But skeptics claim the diary is a forgery,

and point out that in February 1947,

at the time Admiral Byrd was supposedly

visiting this other world underneath the North Pole,

he was actually part of a vast 4,700 man

naval exploration called Operation Highjump

12,000 miles away near the south pole.

But could Byrd's inclusion in this large military operation

at the south pole have been merely a cover story?

Some people claim it was.

And this allowed him to slip away

to the other end of the planet, unnoticed by the media.

GEORGE NOORY: Admiral Byrd, the rumor was,

found a world of flying machines, and people,

and more advanced than us, and that they helped him,

and then he left again.

It's a myth.

Nobody's really been able to prove it,

but it's a great myth.

NARRATOR: Could there really be vast open spaces

within the Earth where advanced civilizations live?

Could extraterrestrial gods really

have come here centuries ago, and hidden the evidence

of their journeys deep within caves and tunnels?

Perhaps we've only just scratched

the surface of our planet's underground mysteries.

If so what clues to our distant past

might still be waiting to be found,

and hiding in the darkness?