All language subtitles for m.f.a.s02e03.1080p.web.h264-cbfm_track3_[eng]

- (birdsong)

NARRATOR: An aerial view
reveals an ancient puzzle.

- Who built it? And why?

NARRATOR: A battlefield mystery
two centuries in the making.

- There's something
really very unusual.

No-one can find the bodies.

NARRATOR: Drone footage
captures a startling sight...

- It almost looks like
a giant pool of blood.

NARRATOR: ..and otherworldly images
from high in the sky.

GEORGE: These dark clouds,
glowing red.

I've never seen anything like this.

- (dramatic music)

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?

- (birdsong)

NARRATOR: A birds-eye-view

can provide valuable
new perspectives of our world,

often uncovering startling realities
that defy expectations.

If it weren't for
this unique vantage,

some of the most
surprising mysteries

might remain hidden
right under our noses...

or more accurately, our feet.

In the American Midwest,
in the town of Newark, Ohio,

lies one such site.

And it happens to be
in the most unlikely of places.

A private golf course.

- If you look down
at the third hole,

you see that the putting green

is surrounded by
this large, circular bank.

- It's about six feet high
and perfectly round.

NARRATOR: While this obstacle

has been challenging golfers
for decades,

it has baffled historians
for much longer.

Because the mound actually
predates the golf course -

by two millennia.

- This mound dates back
to sometime between 100 BCE

and 400 CE,

so it's very old.

- It's clearly not
a natural formation.

Somebody put it here.

But why?

- Who would have built this mound
so long ago

and how did it end up
in the middle of a golf course?

NARRATOR: An even higher look
from above begins to reveal clues.

140 kilometres to the southwest,
in Peebles, Ohio,

there's another
curious earth structure.

NATASHA: Amongst the trees,
we start to see this figure appear.

It looks to be man-made,
but what is it?

NARRATOR: Spanning over 400 metres,

this formation is known
as Serpent Mound.

- It is thought that Serpent Mound
was built around 300 BCE

by the Adena Culture,

the name we give to a diverse
group of pre-contact peoples.

Serpents were considered
supernatural creatures

that were venerated
and often depicted

by ancient North American cultures.

- The theory is that Serpent Mound
was built as an effigy

of this powerful animal spirit,

and was likely used
as a ceremonial site.

- As far as we know, Serpent Mound
is the largest surviving

effigy mound in the world.

NARRATOR: Was the mound at the golf
course built for a similar purpose?

Could it be a ritualistic place

dedicated to a powerful
animal spirit, god, or other deity?

SHEILA: The circle doesn't seem
to be a figurative representation

of a specific animal or being.

But maybe we're missing something.

NARRATOR:
A view from satellites above

starts to reveal a bigger picture.

- When you zoom out
and take a look at this area,

you see that there isn't
just this one circle.

NARRATOR: A short distance
from the third hole

is another circular mound.

Only, this one is much larger.

SHEILA: The second circle is over
a thousand feet in diameter

and encompasses an area of 20 acres.

And it also seems to connect
to a group of straight mounds.

NARRATOR: In total, there are eight
of these linear mounds,

each 168 metres long.

And surprisingly,
when viewed from above,

they form the walls
of a giant octagon.

ROMA: The Octagon spans 50 acres.

That's over two million square feet.

To put that into perspective,

you could fit the Roman Colosseum
into it four times.

NARRATOR: This massive structure
has been called the Circle-Octagon.

And this isn't the only
geometric shape in the area.

Almost two kilometres
southeast of the golf course

is another giant circle.

ROMA: This circular enclosure
is larger than the others.

Fittingly,
it's been called The Great Circle.

NATASHA: Given the size and scale
of these mounds,

this site would have had
a huge cultural

or religious significance
to whoever built it.

NARRATOR: All over the world,

we find evidence
of mysterious ancient sites,

from the famed Stonehenge
in rural England,

to the Mayan ruins of Latin America.

Is this site in the United States

the remnants of another
great and ancient civilisation?

Archaeologists in the area
had the same question.

When they began mapping
these mounds in the 1840s,

what they found was astounding.

- The maps clearly show
the Circle-Octagon

and The Great Circle.

But they also show
that these formations

were actually a part of
a much larger network.

NARRATOR:
Superimposing these early maps

onto current satellite images

shows just how expansive
these earthworks once were.

SHEILA: The maps show
long, connecting corridors

and something called
"The Square".

Its footprint
was almost twice the size

as that of
the Great Pyramid of Egypt.

What these maps clearly indicate

is that this city was built
on top of one of the largest known

geometric earthwork complexes
in the world.

- It must have been a place
of extreme significance,

because it would have taken
an enormous number of workers,

well into the thousands,
to complete this.

And the work likely spanned
multiple generations.

KAREN: Even with today's
modern machinery,

that kind of construction project
would be no small feat.

But 2,000 years ago, they would've
had only the most basic of tools.

NATASHA: Archaeologists have found
primitive hoes in the area,

made from clam shells.

Imagine building these structures
with tools made from shells,

wooden sticks, and animal bones.

It's amazing.

- They would have
likely moved all of that earth

with handwoven baskets,
one by one.

NARRATOR:
Sadly, much of these earthworks

have been destroyed over time.

But certain fragments were adapted
and maintained for modern use,

including the section that was
incorporated into the golf course.

- But the question remains:
Who built it and why?

NARRATOR: Two distinct markings
found on the original maps

may provide the answers.

- The map-makers indicated a path,
or route of some sort,

that branched off from the Octagon,
heading south.

- This path was made
from elongated mounds.

But this wasn't a small footpath.

It was an avenue 200 feet wide.

- Could this be evidence of an
ancient travel route of some sort?

- But who might have travelled these
ancient routes 2,000 years ago?

- They would have been
hunters and gatherers,

and also farmers that lived in
a collection of small communities.

SHEILA: There was a group of people
that lived in the region

between 100 BCE and 500 CE.

They are referred to as
the Hopewell Culture.

NARRATOR: It is believed that the
heartland of the Hopewell Culture

was located 96 kilometres south
of the golf course,

in Chillicothe, Ohio.

Could the route indicated on the map

have once linked
the Newark earthworks

to settlements in the south?

Many believe this to be the case,
that members of the Hopewell culture

were the architects of these
massive geometric earthworks.

A legacy that is recognised
and celebrated

by Native Americans today.

- These were built by my ancestors,
by my forefathers.

What we have today is spectacular.

We have only pieces left,
but try to imagine and try to fathom

what it would've been
had it been preserved and kept.

When you look at these walls,
you can tell the immensity of it.

That's seven million
cubic yards of soil.

The knowledge
that had to go into it,

the enormity of the design.

They had to share
that common vision,

that common desire
to accomplish this.

- But what are these structures for?
And why build them here?

NARRATOR: At first glance,
these earthworks appear to be

a collection of random lines
and shapes.

But with a view from above,
certain patterns emerge.

- The size and orientation
of these mounds aren't accidental.

- For example,
if you look at the Circle-Octagon,

you could draw parallel lines

from the axis points
of the two circles a mile apart.

The corners of the Octagon
and the corners of the Square

also join up
with perfectly parallel lines.

NARRATOR: And researchers
began to wonder whether

this earthen geometry
might correspond to patterns above.

- (animal howls)

- We all know the moon
goes through phases

over the course
of about a month, right?

Every 29-and-a-half days,
you get a full moon.

But the moon goes through
other cycles, too.

Look at where the moon
sets on the horizon.

There are these eight points where
the moon seems to reverse direction

over this thing
called the 18.6 year cycle.

Incredibly,
all eight of those points

are represented in the geometry
of those earth mounds.

And the moon's complex patterns
culminate in this thing

called the extreme
northernmost moonrise,

or the major lunar standstill.

It only happens once in
the whole cycle, every 18.6 years.

And guess what?
When the moon is in this position,

it aligns perfectly along the centre
axis of the Circle-Octagon.

NARRATOR: Is this golf course
in Newark, Ohio,

sitting on top of the world's
largest lunar calendar?

Could it have been a place
for the Hopewell Culture to gather

and bear witness
to the moon's rare standstill?

SHEILA: It's likely that people
came to this site from all over

to witness what was
probably a once-in-a-lifetime event.

The journey here was likely
as important to the Hopewell Culture

as other great pilgrimages
the devout make today.

GLENNA: For 2,000 years,
people gathered here.

This was a central religious place,
a sacred place.

This place was built
because people believed in it,

because there was a power,
because there was a spirit here.

That spirit, that power,
it still exists today.

With Native Americans,
unfortunately,

the word "savages" seems to be
the historical context that we have.

When you stop and realise
the complexity of it,

it could not have been savages
that did this.

They were geniuses.

NARRATOR: And while many
of these earthworks

have been lost over time,

aerial technology
paints a stunning new picture.

Back in Chillicothe, Ohio,

modern LiDAR imaging
detects something extraordinary -

another almost identical
circle-octagon.

- And this one was built
on an exact 90-degree angle

to the one at Newark.

NARRATOR: All this suggests that
the two sites were in fact connected

in a much larger network
of geometric earthworks.

- It's an engineering wonder
that can only be fully appreciated

with a bird's-eye view.

And that's a vantage
we're lucky to have today.

NARRATOR: While a view from above

can showcase humanity's
great capacity for cooperation,

it can also expose
our propensity for conflict.

In Belgium, just south of Brussels,

is the site of another
massive earth mound.

And this one surrounds
a shocking military mystery.

GUY: This is Lion's Mound,

built to commemorate
the Allied victory over the French

in the world-changing
Battle Of Waterloo.

The French Emperor,
Napoleon Bonaparte,

was attempting to conquer
the rest of Europe,

but it was at the Battle Of Waterloo
in 1815 that he lost,

and that puts an end to his reign
and to France's dominance in Europe.

- The battle only lasted a day,
but it killed thousands of people.

- There's something really
very unusual about this battlefield

because despite
the massive loss of life,

no-one can find the bodies.

NARRATOR: Some mysteries
are less about what can be seen

and more about what's missing.

Over the centuries,
Europe has served as the theatre

for countless battles,
not to mention two world wars,

the cost of which is apparent
when viewed from above.

- Europe's former battlefields
are filled with war graves.

These are a truly grim reminder
of the cost of war.

GUY: It's just row upon row
upon row of headstones.

And when you look at it from above,
that gives you a whole appreciation

for this staggering,
shocking loss of life.

NARRATOR:
But the view above Waterloo

is not what you might expect.

- When you compare this site
to other European battlefields,

you can't help but notice

the conspicuous absence
of grave markers.

- What happened to all the soldiers
who lost their lives here?

NARRATOR: Next to Lion's Mound,
in Waterloo's memorial museum,

a macabre relic may offer answers.

Encased in glass
is the skeleton of a soldier

who fought and died at Waterloo.

- This skeleton was unearthed
quite recently, only in 2012.

And this soldier was found with
a musket ball inside his ribcage,

indicating that he was likely shot
and succumbed to a punctured lung.

- Now, there's actually something
really quite special

about this skeleton.

Because this is the only body
to have ever been recovered

from the battlefield at Waterloo.

DAN: Thousands died here
in one day,

and only one body
has ever been found.

How is that possible?

NARRATOR: But there's a group
of battlefield sleuths

determined to dig up clues.

Waterloo Uncovered
is an international team

of volunteers, military veterans,
historians and archaeologists

working to unravel the mystery
of what happened at Waterloo.

- We're looking here for anything
related to the battle,

to help explain this mystery of what
happened to the dead of Waterloo,

which is a very, very significant
historical question.

NARRATOR:
On their quest for answers,

team uses geophysical instruments

that could help them
find lost bodies.

DUNCAN: What we're looking for
is any sort of magnetic anomaly

that stands out from the background.

From that point, we don't know

exactly what the source
of that anomaly is.

So in order to figure that out,
we have to take a sample

and hopefully explain what's causing
that magnetic anomaly.

We've got a pretty dense
concentration of charcoal,

little bits of mortar as well,
it appears.

We've determined this is more likely
to be a pretty modern feature,

so we'll just photograph it,
record it

and move on
to the next anomaly of interest.

- (tense music)

GUY: If you look at the many
battlefield cemeteries

across Europe, you can see that
immense efforts have been made

to honour the dead
and to try to account for

each and every soldier
that was killed.

It is not until the First World War
where you start seeing

memorialisation, commemoration
on an individual level.

NARRATOR:
But a century before World War One,

the Battle Of Waterloo
belonged to a much different era.

- For much of history,
it was common practice

for armies to just leave
the fallen behind.

GUY:
These soldiers typically belonged

to the lowest strata of society.

When you have
overwhelming numbers of dead,

what happens is the bodies
are often just hastily buried

or just left to rot.

NATASHA: But the fact remains,
thousands died here.

You'd expect to find
some trace of them,

especially with today's technology.

NARRATOR: It's a mystery
that has people searching

over two centuries later.

But that can be difficult
200 years after the fact.

- If we examine other battlefields
from the Napoleonic era,

we begin to see clues as to what
might have happened at Waterloo.

NARRATOR:
Just northeast of Vienna, Austria,

is the village of Deutsch-Wagram,

the site of another
deadly Napoleonic battle.

- At the time, the Battle Of Wagram

was the largest battle
in European history.

And just like at Waterloo,

tens of thousands of men
were killed there.

But there's one major difference,
and that's what's been found.

NARRATOR: In 2018,
archaeologists working at Wagram

made a gruesome discovery -
several skeletons

buried just under the topsoil
of a farmer's field.

- Over 50 bodies have been
excavated from the area.

They determined that these bodies

belonged to soldiers
who fought there.

NARRATOR:
And it was found that these soldiers

were clearly buried
in mass unmarked graves.

KAREN: The use of mass graves
was commonplace at the time.

And archaeologists
are finding evidence of this,

not only at Wagram but at
other battle sites of the time.

NARRATOR:
Despite extensive searches,

no mass graves
have been found at Waterloo.

Is it possible that we've been
looking in all the wrong places?

Could the answers be hidden
within Lion's Mound itself?

- The mound is massive.

When it was built, they moved
300,000 cubic metres of soil

from the surrounding area,
and some have wondered

if all this soil doesn't contain
the remains of the fallen.

NARRATOR:
Could this symbol of victory

have also been built
to double as a massive tomb?

- The monument was completed
about a decade after the battle,

so its purpose wasn't to serve
as a container for the dead.

But if there were remains
in the surrounding area,

it's conceivable that some of them

may have been incorporated
into Lion's Mound.

But it still wouldn't account for
all the missing dead.

NARRATOR: Nearby, in a ditch
next to the former battlefield,

Waterloo Uncovered makes
a rare and unnerving discovery -

the remains of three separate legs.

But curiously, these legs aren't
accompanied by full skeletons.

- This particular location
was the site of a field hospital.

And contemporary war diaries
estimate that, during the battle,

some 500 emergency amputations
took place here.

And these leg bones
are evidence of that.

NARRATOR: And more
surprising evidence is found,

including the complete
skeletons of horses.

- When we think about
the casualties of war,

we forget that thousands of horses

have also been killed
as a result of human conflict.

NARRATOR:
Along with these horse skeletons,

the group finds something else
they didn't expect -

a complete set of human remains,

the second body
ever found at Waterloo.

- The story of this particular
soldier remains unclear,

but since his body was found
so close to a field hospital,

he may have died
on the operating table,

with his remains dumped into a pit

used to dispose of amputated limbs
and euthanised horses.

NARRATOR:
If this soldier was put here

by the people
who worked at the field hospital,

who dealt with the thousands of
others who died on the battlefield?

- Battles like this
would leave the countryside

littered with the carnage of war,

and the mess was often left
for the local people to clean up.

Records show that after
the Battle Of Waterloo,

dozens of local peasants were
responsible for this unenviable job.

- But before soldiers' bodies
were disposed of,

they were stripped of valuables
and weapons.

- This sort of scavenging
was rampant.

Clothing, fabric, shoes...

these were
highly valuable commodities

to all the poor at that time.

NARRATOR: But that wasn't the only
thing taken from these soldiers.

At Waterloo, the act
of battlefield scavenging

reached a grisly new level.

- People used pliers to actually
wrench the teeth from the dead

and they then sold those teeth
abroad to make dentures.

And these were known
as "Waterloo teeth".

NARRATOR: After all the pillaging
and pulling of teeth,

what happened
to these casualties of war?

- As far as we know, the majority
of the bodies were disposed of

in much the same way
as other battles of the time -

buried in mass graves, similar
to the ones discovered at Wagram.

NARRATOR: And one likely site for
such burials is Hougoumont farm,

a place of fierce fighting
during the battle.

Historical images depict the use of
mass graves in this very location.

- You have one painting
with mass graves,

with mass graves under construction.

We opened three big trenches
over there

and we didn't find
anything like that.

NARRATOR:
And yet historical accounts suggest

that this site
should be rife with bodies.

- So there on the left, you have
what is called the "Killing Ground".

That stripe of land was covered
with bodies, mainly French bodies.

But we excavated major trenches
over there and nothing,

absolutely nothing.

NARRATOR: Why,
despite graphic historical records

and a widespread search,
have so few bodies been found?

- There are those who believe
the reason

no-one is finding these mass graves
is that the bodies were taken.

KAREN: There's a strong argument
to be made

that the bodies
are no longer in the ground,

and the explanation
is stranger than you might think.

- (birds caw)

NARRATOR: The search for answers
may lead us beyond the battlefields

to an unexpected place -

the vast farmlands
of the British isles.

- Prior to 1840, there was no such
thing as chemical fertiliser.

Before that,
farmers often fertilised their crops

using something called bone meal.

Fertiliser companies
would make this bone meal -

or "dust" as they called it -
by crushing up animal bones.

And one of the biggest markets
for this raw material

was the British Isles.

- We have historical proof
that fertiliser companies

raided other
Napoleonic battlefields,

where they scavenged the bones
of horses and of fallen soldiers.

These bones were then shipped
to bone grinders in the UK.

NARRATOR: The concentration of
phosphorus found in bone mineral

makes it an ideal fertiliser.

It's believed to be
one of the reasons

poppies flourish in Belgian fields,

fed by the remains
of thousands of soldiers

whose bodies were never recovered.

- Now, it's been estimated
that more than a million bushels

of human and animal bones
were imported to Britain

from continental Europe at the time.

- Bones were big business.

And so it's believed
that "bone procurers"

raided the battlefields
in the years after the battle.

- It's almost hard to grasp the idea
that these mass graves

were potentially used
as bone quarries.

But locals easily could have shown
bone traders to the burial sites,

since many of them helped
bury the bodies in the first place.

NARRATOR: While historical records
suggest this practice occurred

at the sites
of other Napoleonic battlefields,

there's no direct evidence to prove

that bones from Waterloo
were used as fertiliser.

If answers aren't to be found
in the fields of the British Isles,

is it possible that the crops
surrounding Lion's Mound

may hold the key?

- This part of Belgium was known
for producing sugar beets,

which are among the most common
plants used to produce white sugar.

To make refined sugar,
these beets were juiced,

and that juice had to be filtered
through something called bone char,

which, as the name suggests,
is also made from ground-up bones.

- And about 20 years
after the battle,

you have this huge sugar factory
being built,

and that's less than three miles
from Lion's Mound.

- If you look at old illustrations
of the factory,

you can clearly see Lion's Mound
in the background.

- Around the same time,
trade in bones took off,

when lawmakers
liberalised the practice.

And there are many written accounts

suggesting the bones of thousands
of horses and countless men

were taken from the battlefield

in order to fuel the country's
growing sugar industry.

DUNCAN: In my opinion, the sugar
beet theory is a strong one.

Now, in order to either support
or refute this theory, of course,

we'd have to find physical evidence
of either an intact mass grave,

or on the other hand,
a grave but it's been emptied out.

This is the sort of thing
we would be looking for

to lend credence to these theories.

NARRATOR: There's no telling
what other secrets may be hidden

deep within these fields.

But if more bodies remain
out on the battlegrounds -

ones that may have evaded
the bone collectors -

the team of Waterloo Uncovered

is determined to continue
their search from above.

NARRATOR: Just when we think
we've seen it all,

a view from above can reveal
something completely unforeseen.

2,000 kilometres from Lion's Mound,

another mystery
is waiting to be solved.

This time
in the Saronic Gulf of Greece.

- This beautiful landscape,

it's dotted with these
picturesque islands

and beautiful white, sandy beaches.

NARRATOR: But in 2021, drone footage
reveals a jarring image.

In the centre of the gulf,
on a small islet called Metopi,

is what appears to be a red lake.

- This red water
looks completely out of place.

- It almost looks like
a giant pool of blood.

Like we found
some kind of crime scene.

- It's really strange.

Why is this lake red?

NARRATOR:
Potential clues may be found

240 kilometres to the north,

in a Greek village
famous for thermal hot springs

that just so happen to run red.

- The name of this village,
"Kokkino Nero",

is Greek for "red water".

NARRATOR: Greece has
more than 700 natural hot springs,

and many of them are believed
to have healing powers.

- And people travel from all over

to bathe in the red water
of Kokkino Nero.

- But most of the country's
hot springs are not red,

so there's something special
about this spot.

DAN: The springs get their colour
from iron oxides in the water.

It's rust. So iron, oxygen, water,

they're all coming together
to make this reddish-brown reaction,

and that's why you get
these iron hydroxides

turning the rocks
and hot springs red.

NARRATOR: Could the red water on
Metopi be fed by a similar source?

- Greece does have hundreds
of known hot springs,

but this water on Metopi
is not one of those.

- No-one comes to bathe or cure
their ailments in this water.

NARRATOR: While some red waters,
like those in Kokkino Nero,

are believed to heal, there are
others that have proven deadly.

Over, 10,000 kilometres away,

at San Angelo State Park
in West Texas,

lies another mysterious red lake.

- Officially it's called
the OC Fisher Reservoir

but it's better known
as the "Texas Blood Lake".

- It seemed like one day these were
healthy waters, with great fishing,

and then the next, it was blood-red,
filled with thousands of dead fish.

- People from various
religious communities saw this

as a sign of end times.

And you have to admit, it does evoke
images of the apocalypse.

NARRATOR: What happened
to these once-thriving waters?

And could something similar
have impacted the island of Metopi?

- The case of the OC Fisher
Reservoir started with a drought,

leaving it almost completely dry.

What little water was left
became stagnant,

and this is when it started
turning blood red.

NARRATOR: This stagnant lake
became a breeding ground

for microorganisms that flourish
in oxygen-deprived waters.

- These microorganisms
belong to a family

known as
the purple sulphur bacteria,

which accounts for the reddish hue
we're seeing.

NARRATOR: But Texas' Blood Lake
isn't the only red water

that would seem to signal
the end of times,

nor is it the strangest.

In Tanzania,
on the African continent,

there's another example
of deadly red waters.

This one even more terrifying.

- If you look at this part
of Tanzania via satellite,

it's unmistakable.

- You see this massive body
of deep-red water.

NARRATOR: This is Lake Natron,

and its waters aren't
the most hospitable.

- First off, the water is hot,

at times, reaching up to
140 degrees Fahrenheit.

To put it in perspective,

that's about 50% hotter

than you'd ever want
in your hot tub.

- But what makes this water
so lethal isn't the temperature,

it's the mineral
and chemical makeup.

- Lake Natron is close to an active
volcano called Ol Doinyo Lengai,

known as "The Mountain Of God",
and it's a very strange volcano.

It's the only volcano on Earth
that spews this dark black lava

called natrocarbonatite,
or "natron" for short.

It turns out it's the coldest
lava in the world,

but it will still burn you.

NARRATOR: This strange lava
formed the bedrock in the area,

giving the lake
its unique composition.

- Lake Natron is highly basic or
what is commonly known as alkaline.

The pH here
can match that of ammonia,

so it's incredibly corrosive
and dangerous.

- Similar to Texas' Blood Lake,

Natron has been turned red
by microorganisms.

In this case, it's an algae
containing red pigments.

And this algae actually thrives
in this extreme environment.

- So the lake's
chemical composition,

coupled with this algae,
has created this caustic red brine.

NARRATOR: This noxious water
will quickly burn the skin and eyes

of most animals
that come into contact with it.

- In the dry season,
when the lake recedes,

you can see all this carnage that's
been hidden below the surface.

But Lake Natron's red water doesn't
just kill unsuspecting animals.

In some cases, it mummifies them.

- Several species of birds, bats,

and other animals
have been found petrified.

- If the Texas Lake of Blood
is like something out of the Bible,

this is more like something
out of Greek mythology.

It's like these animals
have seen Medusa.

DAN:
This lake prevents decomposition

because it turns out that the
chemicals in it are almost identical

to the ones used by ancient
Egyptians for mummification.

NARRATOR: While it's a death trap
to most animals,

the red water of Lake Natron

has allowed
some rare species to flourish,

including 2.5 million
lesser flamingos.

- These flamingos
have tough, scaly legs

that protect them from being burned
by the lake's caustic waters,

and they even have these special
glands in their nasal cavities

that help them
to filter out salt from the water.

- Lesser flamingos also feed off
the algae in the lake.

And it's the same algae
that give the water its red colour

that give the flamingos
their pink plumage.

NARRATOR: Could colourful algae
or other microorganisms

explain the red water
discovered in the Saronic Gulf?

For now,
the answer remains murky,

but the view from above
reveals another puzzling image -

a cryptic inscription emerging
from the bottom of the red lake.

- OK, this just got even stranger.

- Someone has definitely
written something

at the bottom of this lake.

It looks to be
three horizontal lines,

then an "X"
followed by another three lines.

- These look to be letters
from the Greek alphabet.

SHEILA: The three lines do resemble

the 14th letter
in the Greek alphabet.

It's called the letter "xi".

The "X" could be the Greek letter
"chi" followed by another "xi".

- This doesn't spell anything.

Could it possibly be initials
or maybe an acronym for something?

- Could someone have
buried treasure on this island?

Does "X" really mark the spot?

- Or could this be
a simple land marker

placed by whoever owns the land?

NARRATOR: But the question
of who owns this land

isn't an easy one to answer.

- For years, the island was used
for small-scale farming

by people from larger,
neighbouring islands.

And those people all apparently

owned and occupied
small plots of land.

- And so deeds to hundreds
of these small plots

were handed down
from generation to generation.

NATASHA: And it seems that things
may have become fairly acrimonious

amongst the current owners.

None of them can agree
on what to do with the land.

NARRATOR: Perhaps
the peculiar symbol was put there

as a claim to land,
or even a warning.

But how is it that it comes to lie
at the bottom of the lake?

CYLITA: If you look at the island
via satellite,

the water isn't always there.

At times,
it almost seems to disappear.

- This is a shallow lake, and under
the hot Mediterranean sun,

it makes sense that it would
sometimes evaporate.

So someone could have easily made
this mark when the lake was dry.

- So when you pay attention
to the water over time,

the thing that you'll notice is that
this lake is always changing.

Sometimes it's red,
and other times it's milky white.

You know, this change
is almost identical

to what we see in the salt flats
of San Francisco Bay.

NARRATOR:
Could clues to the lake's colour

be found on America's west coast?

Spanning more than
16,000 acres,

the San Francisco Bay
salt ponds are used

in the commercial
harvesting of salt.

- These ponds are massive,
and sometimes they're bright red,

and at other times
they're more white.

- Salt producers gather salt water
in these shallow ponds

by basically just evaporating
all the water off

so that the salt concentration
increases.

And, as that happens,

you get the perfect environment
for salt-loving algae.

- And in order to defend themselves
from the sun's UV radiation,

these algae contain
high levels of beta-carotene,

which is this orangey-red pigment.

So the cycle of salt water pooling,
evaporation,

followed by algae growth
is why we see this change in colour.

And that's what could be happening
here on Metopi.

Perhaps it's a naturally occurring
salt pond.

GEORGE: It makes sense.

Waves would push salt water
onto the island's shores,

then the pooling water evaporates,
increasing the salt concentration.

This is the perfect environment
for red algae to bloom,

creating this red lake.

- All of these changes are happening
on the microscopic scale,

and yet you can see them
from way up above.

- As for the symbol in the lake...
that's still a mystery.

NARRATOR: From a small, uninhabited
island to vast ocean waters,

the view from above
can reveal perplexing sights,

and often when you least expect it.

In 2022, a commercial pilot
flying high above the Pacific Ocean

captured cellphone images
of something very unusual.

- These dark clouds glowing red.
I've never seen anything like this.

GUY: It looks really otherworldly.

It kind of looks like a scene
from War Of The Worlds.

NARRATOR: The origin
of this glowing is unclear,

leaving the pilot and crew
to theorise

over a possible explanation.

- When these images
were posted online,

the internet blew up, with people
theorising about everything

from secret military operations,
even UFOs.

- Before we make the leap
to visitors from outer space,

let's rule out some
more earthly explanations first.

This particular flight was fairly
high up in the Northern Hemisphere.

So could this maybe be
connected to the Northern Lights?

CYLITA: They're called
the Northern Lights

because they appear
in the Earth's Northern Hemisphere.

The closer you are
to the magnetic pole,

the better your chances
of seeing them are.

GEORGE: While the Northern Lights
are most typically green,

the colours can vary depending
upon atmospheric conditions,

and at times they do appear red.

NARRATOR: Could the Aurora Borealis
explain this red luminance

seen from the cockpit?

There's one problem with the theory.

- Typically,
the lowest part of the Aurora

sits about 300-000
to 400,000 feet up.

This plane was flying much lower,
at around 31,000 feet.

So while you might see the Northern
Lights along the horizon

or up higher in the sky,
you wouldn't see them

clustered like this,
directly below the plane.

NARRATOR: If the Aurora Borealis
isn't the answer,

could we be witnessing the effects
of another celestial phenomenon?

- When I see these images,

they almost look like
a Transient Luminous Event.

- Transient Luminous Event,

now that's a term
for upper atmospheric lightning,

and one of the forms it can take
is something called a red sprite.

- Red sprites are huge, sometimes
stretching as long as 31 miles.

- And the reason they're red
is due to molecular nitrogen

emitting low-frequency red light
when it gets excited.

- One of the reasons
they're rarely seen

is because they occur in the
atmosphere above thunderstorms.

So there usually isn't a clear
line of sight from the Earth.

- One thing, though, is that
these sprites travel really fast.

They only appear
for three to five milliseconds.

That's barely enough time
for the human brain

to even register seeing them.

It's nothing like what we see here
that's lasting several minutes.

NARRATOR: While this red light
seems to be anomalous,

it isn't an isolated occurrence.

Another pilot, this time
travelling from Hong Kong

to Anchorage Alaska,

makes an eerily similar discovery.

- In 2014, you get a different pilot
capturing images

that seem to show
exactly the same red glow.

It's really uncanny.

- And this pilot makes his images
public as well,

because he also has no idea
what he's seeing.

NARRATOR:
Images captured eight years apart,

both showing the same
bizarre phenomenon.

Could the two events be related?

- Now, when you look at where
each of these aircraft were

when they saw this red glow,

they were both flying southeast
of Russia's Kamchatka Peninsula.

NARRATOR: Could something
specific to the region

be causing this strange phenomenon?

- The Kamchatka Peninsula
is part of the Pacific Ocean's

infamous "Ring Of Fire".

That's home to three-quarters
of the world's active volcanoes

and this particular area
is a known hot spot.

- They call it Russia's Yellowstone,
and that is for good reason.

- This area has got
at least 29 active volcanoes.

- Were these pilots unknowingly
flying over a volcanic eruption?

- Volcanic islands do exist
in the Pacific Ocean,

but we're not seeing
the plumes of volcanic ash

we'd usually associate
with an eruption.

NARRATOR:
In 2010, a volcano in Iceland

ejected massive plumes
of volcanic ash,

resulting in what, at the time,

was the largest shutdown of air
traffic since the Second World War.

GEORGE: Volcanic ash is a major
safety hazard in airspace.

So if there was an eruption
somewhere inland

or a volcanic island in the ocean
happens to go off,

these planes
would have been rerouted.

NARRATOR:
But not every volcanic eruption

fills the sky
with large clouds of ash.

- It's estimated that 80%
of volcanic eruptions

actually take place under water.

NARRATOR: Is what we're seeing
the result of an underwater volcano?

- Unlike volcanoes
that erupt on land,

underwater volcanoes don't tend to
have the same explosive eruptions.

The pressure of the water from above

keeps the lava
close to the seafloor,

creating something
called a "passive lava flow".

- Also, when the lava makes contact
with the cooler water,

it quickly forms a solid crust.

So it would be unlikely to see
such a large and persistent red glow

on the surface of the water,
let alone from 31,000 feet up.

NARRATOR: If the area's scores
of volcanoes aren't the culprit,

what else might link the phenomenon

to this particular
geographic location?

- Besides being one of the most
seismic places on Earth,

the Kamchatka Peninsula
has another big claim to fame.

It's home to Russia's largest
submarine base.

NARRATOR: Located on
Russia's eastern frontier,

the Rybachiy Nuclear Submarine Base

is home to the country's
Pacific nuclear submarine fleet.

- This area has been crucial
to Russia's strategic defence

and there's long been
a heavy military presence here.

- It's not uncommon for the Russian
Navy to operate in Pacific waters.

It's their backyard.

NARRATOR: The Pacific Ocean
has long been monitored

and used as a testing ground
for the world's superpowers.

- Famously, the United States
used parts of the Pacific

to test nuclear weapons,

in an area they called
the "Pacific Proving Grounds".

NARRATOR: Is this what the pilots
happened to glimpse -

a Russian naval fleet
running a training exercise

or a weapons test?

GUY: If you look at the scale
of this red cluster,

it is perhaps consistent with
a really large-scale naval exercise.

And we also know
that military fleets,

they're often using red lights
to illuminate their ships at night.

But I don't think I've ever seen
a glow quite this bright

coming from any naval vessel.

- And these red lights were seen
outside of Russian waters.

It wouldn't be standard practice
for Russia to have been conducting

unannounced military operations
outside their own territory.

- If this were a military exercise
or a weapon test,

the airways would almost certainly
have been closed

to civilian and commercial aircraft.

So these pilots
should not have been able to fly

directly over that kind of activity.

NARRATOR:
But a closer look from above

indicates another type
of ocean operation.

- Commercial fishing
is big business,

and well over half of the world's
catch comes from the Pacific Ocean.

- A big target for these fisheries
is Pacific saury.

NARRATOR: Saury,
also known as mackerel pike,

is a staple
in many East Asian cuisines,

and there's huge demand
for these fish

in countries including China,
Korea, and Japan.

- And one really effective way
to catch saury is, well...

to use really bright lights.

NARRATOR: Modern fishing vessels
are often equipped

with a large array of LED lights.

When used at night, these lights
attract microscopic algae

and plankton
that are fed on by saury.

TORRI: So, in essence,
these bright lights initiate

an underwater feeding frenzy

that brings the saury up to the
surface for the fishers to catch.

- That is exactly what these pilots
were seeing.

- It's incredible that these
massive red lights

that can be seen
from thousands of feet up

are actually designed
to attract the attention

of microscopic plankton below.

- Yes, the red glow is definitely
a sign of human ingenuity,

but it's also a reminder
of the increasing demands

that people are putting
on the planet.

NARRATOR: Environmental factors
and overfishing have taken a toll

on the migratory patterns
and number of saury in the ocean.

In recent years, Japan's saury haul
was the lowest on record.

CYLITA: As a result of overfishing,

countless species around the globe
are vulnerable,

and our ocean ecosystem is at risk.

NARRATOR: An important reminder
that would have largely gone unseen

if it wasn't for a unique vantage
from above.

- (dramatic music)

NARRATOR: From a strange symbol
etched in red water

to mysterious lights in the ocean...

..and two sets of earthen mounds
an ocean apart...

..the view from above can provide
unexpected insights

into our collective past,
present, and future.

Subtitles by Sky Access Services