Original subtitles

- (tense music)

NARRATOR: Drones spot a vast field

of perfectly pointed stones.

- It's like some kind of weird lunar landscape.

NARRATOR: A massive monolith looming over the surrounding land.

- And it looks totally out of place.

NARRATOR: Hundreds of desolate and crumbing structures.

- What is this place? And what happened here?

NARRATOR: And a vast tower of white plunging off a hillside.

- This is such a strange shape, and it's huge.

NARRATOR: Everywhere we look on our planet,

there's evidence of the past.

In nature.

In buildings.

In relics.

Each holds a mystery

that technology now allows us to see from above.

What new secrets are revealed?

Flying above the landscape, our planet is a rich tapestry

of seemingly endless eternal stone.

From towering peaks, to human handiwork,

rock and stone can hide surprising science and shocking history,

uncovered from the skies.

One stone mystery lies in the Andes mountains

that stretch for thousands of kilometres

along the western coast of South America.

Featuring the tallest peaks in the Western hemisphere.

GEORGE: The Andes are one of the most

mighty mountain chains in the world.

It is the backbone of South America.

NARRATOR: And among the high plateau in Southern Peru,

in the district of Pampachiri...

..drone footage reveals something staggering from above.

- (mysterious music)

- I've never seen a landscape like this.

It's like something out of a fairytale.

- I'm seeing these tall, pointed, rocky spires.

It's like some kind of weird lunar landscape.

- It looks almost like a forest, but the trees are the wrong colour.

How long has this been here?

- These must be some kind of stone or rock,

but why on Earth are they this weird shape?

PETER: How could this have formed?

Is this the work of humans?

Or could this be some strange natural process?

CYLITA: Are there any other strange formations

of rock or stone around the world that could give us a clue?

NARRATOR: There may be a hint just over 6,500 km away,

in New Mexico,

where another landscape holds surprisingly similar shapes

to the forms in Pampachiri.

- These are called the Kasha-Katuwe Tent Rocks,

and it's easy to see why.

They are, in fact, tent shaped.

- And some of these spires can reach

up to 30m in height.

- But how are these unusual shapes formed?

- The secret lies under the nearby Valles Caldera,

in the Jemez Volcanic field.

TIM: A volcanic field is a place

where there's a particular concentration

of eruptive features of some kind.

- (explosion booms) GEORGE: These can form in the area

of a supervolcano.

- And Jemez is a 14-million-year-old supervolcano

that has been shaping the landscape for millennia.

- The supervolcano's most recent eruption

around 1.2 million years ago

created the Valles Caldera... - (explosion boom)

- ..this massive crater in the Earth.

NARRATOR: But how did this supervolcanic power

form the strange peaks at the Tent Rocks?

- About six or seven million years ago,

eruptions in the Jemez volcanic field

spewed ash, pumice and volcanic tuff for miles.

TIM: So, over several million years,

this tremendous thickness of volcanic ash built up,

but it was inter-layered with occasional lava flows...

..material that when it lands,

it can fuse together and form a harder layer,

and those hard layers tend to be thin

relative to the thicker ash.

- This left a layer of deposits over 300m thick.

- Tectonic forces will crack the thin, harder layers.

So they're filled with fractures.

And then as it rains,

water gets down through those cracks

and it begins to erode the softer ash.

But there's a cap of this harder layer.

So you end up with side by side towers,

each one with a little cap on it.

But at some point, it's going to get undercut

and unbalanced, and it will topple off,

and then the spire develops a nice peak on it

so they turn into a nice pointy tent-like shape.

- Rock formations like this are often called

fairy chimneys, or hoodoos.

- So is this what has happened in this area of Peru?

- (mysterious music)

NARRATOR: Could the strange rock shapes in Pampachiri

be connected to an ancient and powerful volcano?

- A look from above reveals that Peru...

..is right on the Ring of Fire,

where the Nazca Plate hits the South American plate.

- So it makes sense to think that volcanic activity

helped create the materials that could,

over millions of years, create this landscape.

- And experts believe that thanks to a volcanic eruption

around four million years ago,

the area became covered in volcanic tuff.

Then over thousands and millions of years,

rain washed away the softer rock,

just like at the Tent Rocks.

NARRATOR: Some experts believe nearby extinct volcanoes

as the likely source of the layers that evolved into the stone forest.

- (in Spanish)

NARRATOR: (in English) So the stone shapes in Pampachiri were formed

in the same way, in an ancient volcanic landscape

shaped by wind and rain.

- And it's a little bit of a goldilocks situation.

These pillars tend to form

in relatively arid regions.

If there's too much rainfall,

everything is carried away and there's no opportunity

for the pillars to form.

But where there's just the right amount of rainfall,

that water gets down through the cracks

in the cap rock and very slowly carries away the fine material

so these pillars develop.

NARRATOR: And incredibly,

this isn't the only one in this region.

- There's actually a volcanic chain

that runs down the spine of Peru in the Andes.

And along this chain,

there are a number of these stone forests.

- And all of these stone forests developed in the same way.

NARRATOR: But there's another shocking mystery here...

..revealed by a closer look... from above.

TORRI: What is happening here?

It looks like something out of Lord of the Rings.

CYLITA: Wait. Are those doors?

I see doors, windows and bricks

at the bottom of these pointed rocks.

PETER: These are houses.

This is something clearly made by people.

- Who could have built these here? And why?

NARRATOR: Perhaps there's an answer

on the other side of the world, in Turkey...

..where another volcanic landscape holds signs of human hands.

TORRI: This is Cappadocia, and it's home

to some of the most stunning fairy chimneys in the world.

PETER: Made of ancient volcanic rock, just like in Peru,

these stones have been integrated into the towns here.

KAREN: Homes are actually built into the rock,

many of them dating back hundreds of years.

NARRATOR: But the rockface hides more than these homes.

- Below the surface are networks of human-made caves,

tunnels, and entire underground cities.

ANTHEA: Some may even date as far back as 1200 BCE,

and it's thought that in the 4th century,

these caves could have been used by Christians fleeing Roman attacks.

KAREN: And these remained in use for centuries -

a haven for locals during raids that spanned

the 600s to the 900s CE.

TORRI: Could these structures in Peru

be some ancient form of protection or defence,

like the Cappadocia caves in Turkey?

GEORGE: Are there any clues as to who could have built

a fortification in this part of Peru?

NARDI: Humans have lived at least periodically in this area

for hundreds, perhaps thousands of years.

And there are signs of historic civilisations nearby.

NARRATOR: 20km to the northeast,

an ancient walled city may offer a clue.

Pikillaqta.

- This ancient city dates from around the late 6th century.

- From above, we can see the city's clear grid pattern.

NARRATOR: This is the trademark sign of an ancient people

known as the Wari.

KAREN: Renowned for their engineering and masonry skills,

the Wari flourished in this region for hundreds of years.

NARRATOR: But could the strange stone village

be connected to the ancient Wari people?

KAREN: The Wari did introduce farming and herding

into this area around 700 CE,

but this village lacks the hallmark grid of Wari planning.

- So who else might be behind these strange houses?

NARRATOR: Even closer, a mere 75km to the north

is the village known as Sondor.

TORRI: This was built around 1080 CE,

by a civilisation known as the Chanka.

ANTHEA: The Chanka are considered a formidable people,

known for their reputation as warriors,

and defensive structures on the high ground of hilltops.

KAREN: Sondor would've been home to several thousand people,

and its fortifications, ramparts, walls, ditches, lookouts,

are formidable.

ANTHEA: Though the Chanka homes in the village

would have been circular stone structures, topped with thatch.

GEORGE: So could these homes in Peru be a similar,

nearly thousand-year-old site, crafted by the Chanka?

CYLITA: It's an interesting idea.

The homes here are definitely round,

but there aren't any of those classic

defensive structures you'd expect.

NARRATOR: So if these aren't ancient fortifications,

what are they?

- Peru is filled with ruins of ancient civilizations,

but could this be a sign of something more modern?

To investigate further, we need to take a closer look.

- It's incredible to find that people actually live here.

It's no abandoned ruin.

ANTHEA: One of the best ways to discover the history

of a place like this is to ask the people who live there.

- (speaking Spanish)

KAREN: (in English) The local family that lives here

reveals that their grandparents created these shelters

to be used for a few months at a time.

- (in Spanish)

NARRATOR: (in English) By carving out these volcanic stone peaks,

and adding stone and mud walls,

these unique dwellings were created.

- (in Spanish)

- (in English) Later, the farming family decided

to live here permanently.

- (in Spanish)

- (grand instrumental music)

GEORGE: It's really amazing how this incredible geological landscape

can form over thousands or millions of years,

and then continue to evolve in a totally new way

as humans discover and explore.

- Who knows what the next 100 years will bring

for this incredible stone forest,

and the village it holds.

NARRATOR: Over 7,00km to the north

in the badlands of Northeastern Wyoming

stands the dramatic landscape of the Black Hills.

- This area was named by the Lakota

for the pine forests that cover its ancient mountain range,

making the hills appear black from a distance.

NARRATOR: But among the trees and hills,

an incredible form reaches into the sky.

- Oh, wow. This is... This is massive.

It really just keeps going, huh?

GEORGE: It's 264 metres from the base to the peak,

and the top covers over 6,000 square metres.

That's a pretty sizable chunk of rock.

- (thunder cracking) NARRATOR: This iconic stone behemoth

is famous for appearing in sci-fi films

and has been a powerful landmark for countless centuries.

KAREN: Many ancestral Native Americans in this area

consider it a sacred place,

known by names such as Bears Lodge,

Tree Rock and Ghost Mountain.

- Today it's commonly known as the Devils Tower,

probably due to a mistranslation of one of those original names.

PETER: It's also a popular site for rock climbers,

with about 5,000 climbers visiting every year.

And no wonder, it's an amazing view.

NARRATOR: Mighty towers of rock like this

are signs of colossal volcanic powers

lurking deep in the Earth.

But there's something strange at Devils Tower.

DAN: You'd expect when there's a big rock formation like this,

that you would see other similar ones all around it,

but there's nothing like it. So, how did this thing form?

ROMA: And why is it so incredibly different

than all the surrounding topography that you can see?

NARRATOR: What clues can we find in the view from above,

to solve a mystery hidden deep in the past,

and far below the Earth's surface?

One hint may lie to the south.

The desert plains of New Mexico...

..where another stand-alone jagged peak

rises high above the sands.

- This incredible rock formation is known as Shiprock.

- Just like Devils Tower, this thing stands alone.

It's unique in its landscape and it's even taller.

It's over 400m high.

- So how did this enormous pillar of rock form?

CYLITA: Hard as it is to believe,

experts think this was shaped underground...

..deep inside a volcano.

- Millions of years ago, the ground level here

was something like 900m higher than it is today.

- And far below, there was a plume of magma

heading toward the surface.

Experts believe that that rising magma

hit a cool groundwater source,

and that combination caused a massive explosion.

CYLITA: That explosion would've created a big crater at the surface.

But not all of the magma escaped.

The magma that became Shiprock

solidified while it was still deep in the neck of the volcano.

- The ash will erode away, but the neck stays,

and that's what Shiprock is.

PETER: And when you look from above,

surrounding Shiprock, you can see these lines

of darker rock radiating out.

- Those are the tops of vertical sheets or dikes

where lava that was in the pipe

broke out into cracks in the rock.

NARRATOR: And the same erosion that revealed Shiprock itself...

..uncovered the dikes once hidden below the surface.

TIM: The combination of those two things

makes this kind of unique, geologically.

I've never seen another formation like this in the world.

NARRATOR: Could that be what happened in Wyoming?

Could the Devils Tower be the remains

of a huge plume of magma

from the neck of an ancient volcano?

CYLITA: It's a possibility.

But there isn't much evidence of a surface

volcanic explosion nearby.

DAN: But there are other magma events

that can create rock formations like this.

NARRATOR: A range of phenomena known as volcanic intrusions.

TIM: Volcanic intrusions are all pretty much the same thing -

they're magma that never made it to the Earth's surface.

DAN: Basically, a bunch of magma

shoves its way up into a layer of rock,

and then hardens while it's still underground.

CYLITA: Over time, those original layers will erode,

and that former magma will stick around longer

because it's harder and stronger.

TIM: If magma is extruded out into a horizontal crack

and cools and hardens,

that's called a sill.

So if you're in New York City and look across to New Jersey

and see those big black cliffs on the other side of the Hudson,

that's the Palisade Sill.

If you get a blister of magma,

so it goes out sideways, but there's enough pressure

that it raises the sediments above it and makes a blister,

we call that a laccolith.

- And over time, those layers on top wear away,

exposing the igneous rock -

rocks that are made by magma.

- So you could picture the Devils Tower forming this way.

NARRATOR: Is a long hidden magma bubble

trapped deep below the Earth the secret behind Devils Tower?

It's one theory, but the view from above

reveals something crucial is missing.

- What's missing at Devils Tower is the sediments

that were bent upwards around the magma,

a ring of upturned sedimentary rocks.

We just don't see that at Devils Tower.

- So what's going on?

NARRATOR: Can a closer look from above offer a clue?

- The rock is all shaped into these massive hexagonal columns.

They look like giant church organ pipes,

or a colossal honeycomb.

- Where else can we find rocks with this unusual geometric pattern?

And what can that reveal about the Devils Tower?

NARRATOR: Over 1,400km to the southwest,

satellites spot a clue in the mountains of California.

This is the Devils Postpile.

PETER: There's a wall of these geometric columns

that stretch from about 12 to 18 metres tall.

GEORGE: And they're polygonal shapes...

..mostly hexagons,

much like the columns at the Devils Tower.

So how was this formed?

TIM: Devils Postpile was an actual lava flow,

basaltic lava that made it out to the surface of the Earth

and flowed sideways,

making a big pond or a lake of lava.

- Around 82,000 years ago,

a volcanic event from the nearby Mammoth Mountain

filled a valley, making a pool

around 120 or so metres deep.

- As this basalt cooled, it contracted.

And because this is basalt,

it really likes to form these hexagonal shapes when it cools.

- And if the lava cools at just the right rate,

cracks will propagate downward through the cooling lava body.

DAN: It can form these shapes in long, even pillars

because it cooled slowly and evenly,

probably over several decades.

CYLITA: Then, thousands of years later,

glaciers travelled through this area.

This carved away one side of the columns,

leaving an exposed wall around 18m high.

DAN: And since we see the same kinds of shapes at Devils Tower,

it makes sense to think that this must have been formed the same way.

Some kind of pool of magma or lava

that cooled evenly and slowly.

GEORGE: But there's a problem.

The Devils Tower isn't made of basalt.

It's actually formed of something called phonolite porphyry.

- (hawk screeches)

CYLITA: The good news is that phonolite is a kind of igneous rock,

meaning it was formed by cooling magma or lava.

- So the question is,

what conditions can make the phonolite make columns

just like basalt at the Devils Postpile?

- Actually, columnar jointing can happen in any igneous rock

if it cools at the perfect rate.

- So can these phonolite columns

tell us exactly how the Devils Tower formed?

- Not exactly. Under the right conditions,

columns could form wherever an intrusion of magma happened to cool.

CYLITA: But there is one more amazing location

that might provide an explanation of what happened here.

NARRATOR: On the other side of the Atlantic in the Czech Republic,

the view from above reveals a massive rock

breaking out from the rolling green hills.

- This is known as Boren It's a rock formation

that has some key similarities with the Devils Tower.

- It's made of phonolite, too.

And it has some notable columnar jointing.

- So how did this form?

PETER: It's actually thought to be similar to the event

that created the Shiprock in New Mexico.

A massive volcanic event with magma that exploded

as it interacted with groundwater.

- But instead of the remaining pinnacle being deep in the volcano,

it formed part of the lava

that rose into the debris-filled crater at the top.

CYLITA: The magma cooled and hardened under the debris,

then over millions of years, that debris wore away,

leaving this tower of rock behind.

NARRATOR: Could this be the secret?

Is the Devils Tower all that remains

of an ancient volcanic crater?

TIM: With this kind of eruption,

you end up with a lot of ejecta,

stuff gets thrown everywhere.

We don't see that at Devils Tower.

NARRATOR: But could signs of a massive ancient eruption

simply... disappear?

GEORGE: It's possible.

The dating that's been done on the Devils Tower

identifies it as being around 50 million years old.

That's plenty of time for even the huge amounts of land

we're talking about to change.

- It's awesome to imagine how the land might've looked

with this massive monolith sitting in a huge crater

filled with volcanic debris and lava.

And then over millions of years,

wind and rain erode everything else away

until all you're left with is this epic tower.

NARRATOR: So what's the truth behind this ancient natural monument?

- This is a really hard problem.

TIM: I'm convinced that it's a volcanic neck,

but that leaves a lot of things wide open.

- In all of these theories, erosion is key

to revealing the Devils Tower...

but that same process

has erased much of the evidence that we need

to determine what actually happened here.

TIM: We could probably learn more

if we sampled the heck out of Devils Tower,

but nobody wants to destroy this thing of beauty

to figure out exactly what it is.

So, let's leave it a mystery.

NARRATOR: Along the Mediterranean coast of Turkey...

just outside the city of Fethiye...

..the view from above reveals something strange

in the hills.

ANTHEA: What happened here?

This is a really eerie, sad-looking site.

- Locals know this place as Kayakoy,

or Rock Village, and you can see why.

NARRATOR: These ruins cover around 33 hectares,

about three times the size of Ellis Island.

- What is this place? And what happened here?

- Who built these structures? And why did they leave them behind?

GUY: Is this some kind of ancient ruin

or the site of some kind of disaster?

KAREN: And even stranger,

this is on the outskirts of the tourist hotspot of Fethiye

- Plenty of people live and travel right around here.

GUY: So, the big mystery is this,

why is this area completely abandoned?

NARRATOR: A hint may lie almost 2,000km to the northwest...

in Switzerland.

When a crisis hits the tiny village of Brienz/Brinzauls.

- In May of 2023, this tiny Swiss village

was warned that a disaster was imminent.

- A huge mountain of unstable rock sits next to the village,

and for decades, was the site of movement

and occasional falling rocks.

- Scientists had been watching that spot for a long time.

There was all kinds of monitoring going on.

So they could see that that piece of mountain was moving.

- In the spring, movement began to accelerate.

Emergency plans sprang into motion and the residents were evacuated.

- Only a few weeks later,

on the night of June the 15th to 16th,

that this landslide was just unleashed.

Over one million cubic metres of rock

just hurtling, plummeting towards the village.

- The following morning, footage from above revealed

the dramatic landslide,

and the incredible realisation

that the village had been spared.

- (dramatic music)

- Could something similar have happened here in Turkey?

Was this village abandoned during a sudden natural disaster?

NARRATOR: Is this the site of a crisis so devastating

the inhabitants could never return?

Turkey is known for one particular kind of catastrophe.

- That would be earthquakes.

- Turkey has thousands of earthquakes every year,

and that's because of what lies under the surface.

TORRI: Turkey is absolutely covered in active fault lines,

because it sits at the intersection

of five different tectonic plates,

all pushing in different directions.

TIM: Turkey is being squeezed.

The stresses build up, and then they pop.

So virtually all of Turkey is earthquake prone.

- And when we look at an earthquake hazard map,

we can see that Kayakoy is in something of a hot zone.

- So you have to ask, was Kayakoy actually abandoned

during some historic earthquake?

I mean, is that going to explain all this destruction?

NARRATOR: A clue lies in the nearby town of Fethiye.

And only a few decades in the past...

..when disaster strikes.

NATASHA: In April of 1957,

the area is struck with a double whammy.

Two powerful earthquakes rock the region mere hours apart.

ANTHEA: Photos from the time show the utter devastation.

It was so severe that the city essentially had to be rebuilt.

KAREN: That rebuilding was actually what led

to Fethiye embracing the tourism industry which thrives today.

NARRATOR: But was nearby Kayakoy abandoned

during this devastating earthquake?

GUY: So that earthquake in 1957,

that destroys most of Kayakoy's buildings,

but it doesn't find that it enjoys

the same revamp that Fethiye gets.

So why is Kayakoy left in complete shambles?

- Archive images reveal it's because this village

had already been abandoned.

SHEILA: But why? What could have happened

before this devastation that was so serious

that the people never returned, and it was never rebuilt?

NARRATOR: There may be a clue just off the coast of Kayakoy,

where a modest island holds an astonishing history.

KAREN: This is Gemiler Island

and it's pretty tiny -

only around 1km long and 400m wide.

NATASHA: But while all you can see today are some stone ruins,

these actually hold a pretty amazing history.

ANTHEA: Many of these buildings are actually religious structures.

Chapels, basilicas, and tombs.

Some date back to around the 4th century.

KAREN: Evidence suggests that this was an important religious

pilgrimage site for Christians,

possibly because it was a saint's shrine.

But which saint?

NATASHA: Some researchers think this was actually

the resting place of Saint Nicholas - Santa Claus.

NARRATOR: Ravaged by time,

there is one possible clue to this holy mystery.

- There is a fresco in one of the churches that reads

‘Hossios Nikolaos'.

And if nothing else it was likely built to honour Saint Nick.

- It's thought that this holy site was abandoned

following attacks by Arab forces around 650 CE.

ANTHEA: This makes sense,

as the 7th century saw the beginnings of the Arab conquest

that would eventually spread throughout

the Middle East and North Africa.

- But what happened to the people who lived on this holy island?

NATASHA: It's believed that they actually fled

to what is now known as Kayakoy.

TORRI: So could these two events be connected?

Were the people of Kayakoy fleeing raiders?

SHEILA: Or is there some religious connection?

Can we find any clues in the abandoned village itself?

NARRATOR: A closer look from above reveals two crucial clues.

- There are two churches here, both Greek Orthodox.

ANTHEA: But this is Turkey.

Something like 99% of the country is Muslim.

So why are there two churches for an area

with some three to four hundred houses?

NATASHA: There must have been a pretty decent sized

Christian population...

but when? And where did they go?

NARRATOR: For centuries, Christians and Muslims

lived in this village side by side,

under the powerful Ottoman empire.

- With a Christian settlement on the hillside,

and a Muslim settlement in the valley below.

- So when did the Christian area become the abandoned Kayakoy?

- It's all tied to a terrifying chapter in this region's history.

- (explosions booming)

TORRI: The Ottoman Empire was facing serious pressure,

fresh from the Balkan Wars against Serbia,

Montenegro, Bulgaria and crucially Greece

when World War I began.

- Facing external pressure and internal revolts,

the Ottomans joined World War I

on the side of the Central Powers,

hoping in part to keep their Empire from total collapse.

- Whether from suspicion of collusion or revenge,

Greek Christians living in the Ottoman Empire were targeted,

and in 1914, what became known as the Greek Genocide began.

SHEILA: Greeks were forced from their homes, attacked,

deported, raped and killed.

This continued throughout the World War.

Hundreds of thousands were killed or displaced.

NARRATOR: But the Ottomans were on the losing side,

so what happened when the Allies won the war?

- After that conflict ended,

Greece then attacks the Ottoman Empire.

Now, this war leads to the collapse of the empire

and the creation of Turkey under the military leader Kemal Ataturk,

and he successfully routed the Greek invasion.

NARRATOR: But what did this victorious new leader have in store

for the surviving Greeks in Turkey?

- That war ended with something called the Treaty of Lausanne,

which, among other things, dictated a massive population swap.

NARRATOR: At least 1.5 million people were moved.

SHEILA: Turks from Greece were sent to the new country of Turkey,

and remaining Greeks in Turkey were sent to Greece.

NARRATOR: So how did these tragedies

change the shape of this quiet seaside village?

- Just like the rest of the country, the Greek population of Kayakoy

was subject to abuse and deportation.

TORRI: In September of 1922,

Ottoman authorities ordered the evacuation of Kayakoy,

the village that was then called Livissi.

And in 1923, Muslims were brought from northern Greece

to the now-abandoned village.

NARRATOR: But why did these homes remain empty?

GUY: So when you have these Muslim Turks

who had been exchanged from Greece,

when they arrive, they don't want to live

in the abandoned houses in Kayakoy.

ANTHEA: These new inhabitants were farmers,

and there wasn't enough suitable land around Livissi for cultivation.

- So the area actually never recovered from the exodus.

NARRATOR: And the village of Livissi remained abandoned

and became the Rock Village of Kayakoy.

- And the crumbling homes now stand as monuments

of the tragic and brutal past.

SHEILA: Whenever I'm looking at ruins and abandoned sites,

I think of them as scars on the landscape.

And scars always tell a story, don't they?

KAREN: Sites such as these, sad as they are,

are so important.

By investigating their history,

we remember and honour important parts of our past,

and hopefully learn how to never repeat them.

NARRATOR: Looking down at the mountains of southern Mexico,

around 50km outside Oaxaca...

..in the surrounding mountain cliffs,

the view from above reveals a staggering feature

thrusting off one peak.

- Oh wow, this looks so dramatic.

- This is just beautiful.

- It looks like a massive waterfall

cascading off these deep red cliffs.

NARRATOR: Waterfalls are some of the most stunning

natural features in the world.

And many are beloved landmarks.

But there's something unique about this site.

This waterfall is made of stone.

- (mysterious music)

- It looks like a waterfall that's frozen in time.

What an incredible illusion, though.

How does stone appear to ripple down the cliff-side

without actually moving?

- What's it made of exactly?

- And how was it formed?

GEORGE: Are there any clues to be found

around this unusual rock formation?

NARRATOR: A closer look from above reveals a hint.

- It may not be a waterfall, but there is water here.

ROMA: There's a series of shallow pools at the top of this plateau.

And some of them are some really interesting colours.

GEORGE: Locals call this place Hierve el Agua.

It means "boil the water" in Spanish.

PETER: And if we take a closer look, you can see why.

The water here is bubbling.

So what could be going on here?

NARRATOR: Perhaps a clue can be found over 12,000km away...

..in the canyons of southern Armenia...

..where a serene mountain spa

holds the Jermuk Hot Springs.

- There are over 40 hot and cold springs at Jermuk,

ranging in temperature and size.

PETER: The geysers are full of carbon hydro-sulphate-sodium

and minerals like potassium and magnesium.

SHEILA: But can these mineral-rich natural hot tubs

give us any clues about the waters at Hierve el Agua?

- Just like in Jermuk, these are natural hot springs.

NARRATOR: Could that mean there is something hiding in the water?

- Warm waters are always going to have minerals in them

because the warmer the water is,

the more likely it's going to dissolve

whatever it comes in contact with.

- And the colours here can provide clues as to what's in the water.

TIM: The colour of the water is not so much affected

by the dissolved material in it,

but by very fine suspended material.

It would be the same thing as putting cocoa powder into milk.

The cocoa doesn't actually dissolve,

but that powder, those tiny, tiny grains,

stay suspended and turn the milk brown.

ROMA: What stands out to me is there's a few larger springs

that appear a turquoise colour.

And this is an important clue.

NARRATOR: What could make this water turn this striking shade?

- This colour of water usually indicates

a form of limestone leaching into the water.

PETER: And that is a sign of the dominant mineral here,

calcium carbonate.

That's a chemical compound that commonly appears in rocks

and is also the main component in seashells,

pearls, eggshells and heartburn tablets.

- But what can that tell us about the creation

of this weird stone waterfall formation?

Can similar rock shapes anywhere offer a clue?

NARRATOR: Almost 2,000km northwards...

..in New Mexico,

the rugged Chihuahuan Desert hides a hint below the surface.

- From above, you can see the entrance to the Carlsbad Caverns,

a labyrinth of over 300 limestone caves

sitting in the desert here.

- Formed over 250 million years ago,

these grottos are brimming with magnificent natural features.

- The wet, mineral-rich environment makes it easy

for a range of rock formations,

known as speleothems, to flourish.

- They're all related to rainwater

picking up ions in the rock

and then redepositing them when they emerge in the cave.

- Some of the most famous are stalactites and stalagmites.

- Stalactites form when the groundwater

that's saturated in calcite from the limestone

drips down through the cave ceiling,

then the water evaporates off

and leaves the minerals behind.

CYLITA: he calcite then deposits in different places,

and builds up over time,

forming stalactites that hang from the ceiling.

- And then, similarly, stalagmites are formed basically

the same way, except the water drips to the floor of the cave.

And then you get these jagged mounds that grow upwards.

- Often, where there's a drip from the ceiling,

there's a stalactite growing down from the ceiling,

and a stalagmite growing up from the floor,

and they can meet and form a column.

- And these speleothems at Carlsbad

look pretty similar to the cliff-side at Hierve el Agua.

- But can this happen outside, on a cliff-top?

NARRATOR: The answer may be found almost 11,000km away...

..in southwestern Turkey...

..where the view from above reveals

the rolling white hills of Pamukkale.

- Pamukkale means, "cotton castle" or "cotton palace"

and you can see how it gets the name.

DAN: The area features around 12 square kilometres

of terraced basins nestled in thick white limestone.

NARRATOR: And a closer look at these cloudlike rocks

reveals some similar shapes.

- It looks like an outdoor cave,

a mineral forest laden with stalactites and stalagmites.

- But how do these form outside of a cave environment?

DAN: It's pretty much the same way they form inside.

It's the combination of water and limestone.

The water carries away the calcite from the dissolving limestone

and deposits it somewhere else.

NARRATOR: And here in Pamukkale,

the view from above reveals a smoking gun.

- The calcite deposits can just naturally form

in a way that resembles cascading water.

DAN: The blindingly white facade is created

by the continuous fresh deposits of calcite-laden water

from the surrounding hot springs.

NARRATOR: As the spring water emerges from the ground,

it evaporates, leaving the mineral behind.

TIM: And that builds up a little bit of a dam.

So the water begins to pool behind that,

and where it spills over the dam,

the dam grows higher and higher and higher.

NARRATOR: As the water continues to flow downwards,

more dams form.

- So they develop a series of steps.

ROMA: Creating these petrified waterfalls

we can see here at Pamukkale.

So could this geological process

explain the striking cliff-side features in rural Oaxaca?

- (birds chirping)

TIM: The difference between the frozen waterfall in Mexico

and Pamukkale is the slope

of the hillside or the mountain that they're coming down.

In Mexico, it's on a very steep hillside.

- This amazing site in Mexico

is created by the same kind of really unusual

geological processes.

NARRATOR: Deep in the Earth,

spring water travels through limestone terrain.

- If this flow path goes deep enough,

it's going to make that water warm,

because the deeper you go in the Earth,

the warmer it gets.

NARRATOR: This warm water dissolves some of the limestone,

and carries it along its path, until it reaches the surface.

- As the water emerges at the surface,

it reacts with the air,

and those dissolved minerals drop out of the water.

- So over thousands of years,

layers and layers of calcite from the spring water

settles into its new home on the cliff face,

in the shapes dictated by the movement of the water.

- It's really just nature rearranging the furniture.

CYLITA: The power of water is spectacular.

What it can build and create, how it can destroy,

and how it can change the landscape, like what we see here.

TIM: It looks impossible that nature made something like this,

but it's all perfectly natural, but looks like art.

DAN: These unique and picturesque petrified waterfalls

are a perfect reminder of how geological processes

continue to churn away on our planet every single day.

NARRATOR: From ancient formations shaped through thousands of years,

to handmade work within stone,

ageless rock can hold human stories

and the secrets of the Earth's own history,

all ready to be uncovered

in the view from above.

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