Original subtitles

Narrator: A flash flood high in the Himalayas devastates

a small mountain village.

Dr. Leonard: Raini was leveled, and when all was said and done,

more than 200 people lost their lives.

James Ellis: Flash flooding in the Himalayas

is fairly common during the summer.

But this happened in February. So what happened?

Narrator: Evidence of an ancient battle is unearthed

on the banks of a river in Northern Germany.

Dr. Agbedor: Roughly 12,500 bones were excavated,

belonging to about 150 individuals.

Dr. Cantor: Do the math, and it's like

a scene from a horror movie.

Narrator: A mysterious ghost town is explored

in Russia's Caucasus Mountains

Anthea Nardi: The area is eerie and quiet,

and looks like it hasn't been inhabited for hundreds of years.

What is this mysterious, abandoned city?

♪ [show theme music]

Narrator: These are the strangest mysteries,

trapped in the coldest places.

♪♪

Lost relics.

♪♪

Forgotten treasures.

♪♪

Dark secrets.

♪♪

Locked in their icy tombs for ages.

But now, as ice melts around the world,

♪♪

their stories will finally be exposed.

♪♪

♪♪

Narrator: The North Indian state of Uttarakhand

covers roughly 20,000 square miles

and contains many towering, snow-capped peaks

of the Himalayan mountains.

Dr. Leonard: Some of the tallest mountains in the world

are in Uttarakhand, including Nanda Devi,

which at over 25,000 feet,

is the second-highest peak in India,

and the highest located entirely within the country.

James Ellis: The Himalayas are home to the third largest

accumulation of ice and snow in the world,

behind only Antarctica and the Arctic.

There are roughly 15,000 glaciers

scattered throughout the range

and over 1,400 of them can be found in Uttarakhand.

Dr. Riskin: In the northern region of the state,

10 to 15 feet of snowfall is typical

between December and March.

January is the coldest month,

when the temperature never gets above freezing.

Dr. Cantor: Uttarakhand is the most populous

of the 11 Indian Himalayan states,

there are roughly 10 million people there,

the majority of whom live in the more than

16,000 villages that dot the state.

Narrator: Residents of Raini, a small mountain village

located on the banks, at the confluence

of the Rishiganga and Dhauliganga rivers

are going about their daily business

when suddenly, disaster strikes.

Dr. Leonard: Out of nowhere, a massive flash flood

swept through the village,

obliterating everything in its path.

Raini was leveled, and when all was said and done,

more than 200 people lost their lives.

James Ellis: Flash flooding in the Himalayas

is fairly common during the summer,

as heavy rains and melting snow combine.

But this happened in February and events like this

are highly uncommon so early in the year.

So what caused this devastating flood?

Dr. Cantor: It could've been what's called

a Glacial Lake Outburst Flood or GLOF, which happens

when a sudden release of water from a glacier

results in a swift downstream flow.

In the Himalayas, large bodies of meltwater can form

in front of glaciers and even break free,

causing a flash flood.

Sometimes these events are thought to be

caused by earthquakes.

Narrator: In October of 2023, Nepal experienced

four earthquakes in a single hour.

The next day, an outburst from South Lhonak Lake

in northwestern India led to a catastrophic flash flood

in the Teesta River basin,

resulting in multiple fatalities.

Dr. Riskin: Some glacial lakes are dammed by moraine banks.

Basically, you've got material like soil and rocks,

that's been left behind by a moving glacier,

and it is not stable at all.

It can be easily broken up by even a small earthquake.

So when that happens, it unleashes a torrent of water.

Could an event like that have caused the flood

that devastated Rainy?

James Ellis: Probably not. The theory that earthquakes

can cause Glacial Lake Outburst Floods

has been challenged recently

and most of the evidence supporting it is anecdotal.

One recent study of 59 earthquakes in the Andes

between 1900 and 2021 that occurred in the vicinity

of known glacier lakes,

found that only one had triggered

a Glacial Lake Outburst Flood.

Dr. Leonard: In the aftermath of the Nepal earthquakes

and the ensuing flood, authorities were unable

to definitively connect the two events.

So while it may seem like an improbable coincidence,

there's no concrete proof that the earthquake caused

South Lhonak Lake to burst.

But GLOFs can be caused by other factors,

like heavy, sudden rainfall.

[loud thunder]

Narrator: In June of 2013, a cloudburst in the upper regions

of the Himalayas in Uttarakhand

led to flash floods that killed over 6,000 people

and swept away scores of villages and towns.

The worst hit region was around the sacred Kedarnath shrine,

and the flood occurred during the height

of the pilgrimage season

when the area was teeming with visitors.

It has been described as the worst natural disaster

the state has ever endured.

Dr. Riskin: Almost 13,000 feet up,

Chorabari Glacier received 440% more rain

over several days, than it normally gets.

Like instead of 2.7 inches, it got 15 inches.

That caused meltwater to accumulate,

and that, along with the rainwater itself,

overwhelmed Chorabari Lake,

which sits at the end of the glacier.

Dr. Cantor: It was described as the lake "exploding",

and the rush of water caused some river levels to rise

by almost 40 feet in the downstream areas.

The debris load consisted of huge boulders,

some with a diameter of up to 32 feet!

It was total destruction for anything in the flood's path.

James Ellis: Multi-story buildings, bridges, and roads

were swept away as severely swollen rivers

tore through Uttarakhand,

burying entire villages in debris and silt.

Over 100,000 people who were trapped in inaccessible areas,

cut off by destroyed roads and landslides,

were rescued by the army and civilian volunteers.

All of this devastation was caused by excessive rainfall.

So could that have happened to trigger the flood

that destroyed Raini?

Dr. Leonard: It's possible, but the Raini flood happened

in February, and the rainy season is in the summer,

so it's unlikely there was significant rainfall

at that time.

Also, satellite imagery from before and after the flooding,

showed it was probably not triggered by a glacial

lake breech, because no lakes were visible in the area.

Something else must have caused the flood.

Maybe something man-made?

♪♪

Narrator: In October of 1965,

an expedition of American and Indian climbers,

hauled seven plutonium capsules and surveillance equipment,

up the slopes of Nanda Devi,

with the intention of positioning them

on the top of the mountain.

The mission was orchestrated by the CIA,

and the Indian government's Intelligence Bureau.

Dr. Riskin: As crazy as this might sound,

the idea was to put nuclear- powered monitoring instruments

in the Himalayas, to spy on the Chinese nuclear weapons testing.

This is the height of the Cold War.

No idea is off the table, in terms of how expensive,

or outrageous it might sound today.

But it also tells you how remote this place is.

They're talking about using nuclear power.

That is what you use if you're powering an instrument

on another planet.

And this place is almost that remote.

Dr. Cantor: Bad weather forced the climbers to abandon

the mission short of the peak.

And on their way down, they left the instruments behind.

Two radio communication systems,

a six-foot-long antenna,

a power pack, and the plutonium capsules.

But when they came back the next year

to try to complete the mission, everything was gone.

Dr. Leonard: Here's where things get a bit weird.

Some residents of Raini believed

that the flood was triggered by an explosion

of the nuclear material left on Nanda Devi.

Some reported an overpowering smell in the air,

as debris from the mountain inundated the village

and their theory is that the plutonium was buried

under the snowpack, radiating heat,

and somehow that caused the flood.

James Ellis: I suppose anything's possible,

but the plutonium was in a sealed capsule,

so it's highly unlikely to leak.

And the odds of something like that triggering a calamity

of this magnitude, are pretty astronomical.

Narrator: Hoping to get to the bottom of the mystery,

an international team of over 50 researchers

begin to analyze several different data sources,

including field observations and satellite imagery

of the mountainous area above Raini.

Before long, they have their answer.

Dr. Cantor: The satellite images show that near the top

of the 19,500 foot Bronte Peak,

a huge chunk of ice covered rocks suddenly collapsed.

950 million cubic feet of material was released.

And when it hit the rocky floor below,

the energy released was equivalent to 15 times that of

the atomic bomb dropped on Hiroshima in World War Two.

Dr. Riskin: The ratio of rock to ice was around 80/20,

and that ratio, combined with a fall of over a mile,

generated enough heat from the rocks rubbing together,

to almost completely melt the glacial ice,

and turn all of it into a massive torrent of water.

When that debris flow crashed through the Rishi Ganga

hydroelectric plant, about nine miles from Raini,

it was traveling over 55 miles an hour!

J. Ellis: Six miles downstream from the Rishiganga plant,

the Tapovan hydro facility was also destroyed,

and to make a bad situation even worse,

the floodwaters burst open a dam,

adding even more water to the bedlam.

Dr. Leonard: In total, 204 people lost their lives

in the disaster, most of them either

working in or visiting the power plants.

It's believed that a part of the glacier that caused the collapse

was hanging on a mass of rock, and weakened

over a long period of freezing and thawing.

Eventually, the laws of physics won out

and triggered this tragic event.

Narrator: Following the disaster,

a new flood warning system was installed near Raini.

Hopefully, this sleepy little mountain village,

will never have to face this kind of tragedy again.

♪♪

Narrator: In the Northeast corner of Germany,

the state of Mecklenburg-West Pomerania is shaped

and scarred by millennia of glacial activity

and harsh nomadic climates.

Today, it is still one of Germany's coldest regions.

Dr. Leonard: The area is bordered to the North

by the Baltic Sea, which can have a temperate effect,

so the summers are cool and wet.

But the winters can get absolutely punishing.

The coldest temperature on record plummeted to

-26.5 degrees Fahrenheit in 1929.

Dr. Cantor: The northern section of Mecklenburg-Vorpommern,

or Mecklenburg-West Pomerania

contains thousands of rivers formed in the aftermath

of the last Ice Age.

One of the largest of these, the Tollense,

twists and turns for 40 miles in a snake-like pattern

along the marshy Tollense Valley.

Dr. Agbedor: The cold temperatures and wet climate

of the Tollense Valley marshes

have been ideal for preservation,

and have recently made it a focal point for archeologists

hoping to learn more about the area's rich history.

Narrator: An amateur archeologist is paddling

his canoe through a marshy section of the Tollense River,

when he makes a surprising discovery.

James Ellis: He spotted a number of human bones.

They were splayed out from the riverbed,

just a few feet from the water.

But the biggest surprise was yet to come.

Dr. Leonard: He called his son over to help him

retrieve one of the bones,

a right upper arm bone, known as the 'humerus.'

And jutting out of the bone was a flint arrowhead,

embedded deep in the shoulder joint. Ouch!

Dr. Cantor: The two of them continued to scope the area,

and they also found a wooden club,

about the size of a baseball bat.

On first inspection, there was no way to tell

how old these items were.

But the shape of the club and the arrowhead

show that this is no 'modern' crime scene!

Where did these bones come from?

And more importantly, were there more of them?

Narrator: The discovery in the Tollense River,

sparks a series of excavations by teams of archeologists,

curious to uncover the bones' origins.

What they find, shocks even the most experienced

of the scientists.

Dr. Agbedor: A section of the riverbed

measuring over a mile long,

was practically overflowing with human remains!

Roughly 12,500 bones were excavated,

belonging to about 150 individuals.

The bones were embedded in sediment between

3 and 6 feet below the surface,

which is not very deep.

James Ellis: The remains were scattered and disarticulated,

making it challenging to identify "whole"

or complete bodies, since they weren't preserved

in their anatomically correct positions.

Dr. Leonard: While the remains were found consistently

along the one mile length of the riverbed,

most of the bones were concentrated at two main sites,

"Weltzin 20" and "Weltzin 32."

Weltzin 20 had the highest concentration,

a density of one individual per 12 square feet.

Dr. Cantor: Do the math, and it's like a scene

from a horror movie.

The hero is suddenly surrounded by hundreds of skeletons!

So what exactly is this site, and what happened here?

Was it a mass grave, or a flooded cemetery?

Or did all these bones collect in the same spot

over hundreds of years?

Narrator: A team of researchers took samples

from multiple sites for analysis and testing.

Dr. Agbedor: The radiocarbon dating test found

that the bone samples could be traced to 1200 BC,

with a margin of just plus or minus 40 years.

The average taken from nine bone samples was 1230 BC.

That's over 3,000 years old!

Dr. Leonard: During that time, northern Germany

was mostly populated by farmers and tradesmen,

who were engaged in both the production

and the export of bronze items.

So many of the people who lived here had the metalworking skills

to create artifacts and trade with other neighboring regions

such as Bavaria, Bohemia and Saxony.

Narrator: As the archeologists continue to work

on the Tollense sites, they uncover several bronze items

along with the human remains,

including a ring,

a belt box, armbands,

and multiple arrowheads.

Dr. Cantor: So they had a good idea

of who these people were,

backed up by physical evidence from the site.

But the concentration of all those bones

in such a small area, was still a mystery.

Dr. Agbedor: It wasn't the only time a discovery

of multiple Bronze Age human remains was made in Germany.

In 2001, near the Southwestern town of Neckarsulm,

a construction crew was excavating a site

for an industrial park,

when they uncovered a massive burial ground.

James Ellis: There was no shortage of bodies to examine.

In fact, there were several "multiple" burials.

50 individuals were found in 32 graves!

There were eight double graves,

there were three with three individuals,

and one example of five people buried together!

Dr. Leonard: Experts also uncovered a treasure trove

of grave goods from the late Bronze Age

buried along with the bodies,

including ceramic vessels, cloak pins, razors and swords.

Based on their analysis they were able to determine

the deceased were placed here over a period of 50 years,

so roughly two full generations.

Narrator: Experts at the Tollense site consider

the possibility that it was once a Bronze Age burial ground.

Dr. Agbedor: But there were a few fundamental problems

with the "mass grave" theory.

First of all, there was no indication of any other objects,

or artifacts typically associated with burial sites

from that period, such as pottery or ceremonial jewelry.

James Ellis: Plus the radiocarbon dating of the bones

was very specific - 1230 BCE,

with a narrow margin on either side.

This means the bodies weren't placed here

over centuries, or even decades.

These hundreds of individuals all died

from a single major event. But what could it have been?

Narrator: To look for clues,

including a possible cause of death,

scientists examine a wide cross-section

of the skeletal remains.

Dr. Leonard: Several skulls had obvious lesions and injuries

that were inflicted at, or right before, the time of death.

A few of these were from blunt force trauma,

but most were caused by a sharp instrument or weapon.

One skull exhibited a lesion on the right parietal bone,

a small hole that experts believed was caused

by an arrowhead shot from a distance.

Dr. Cantor: These injuries were consistent with the weapons

found at the site: wooden clubs, swords, sickles,

and hundreds of flint and bronze arrowheads.

One skull cap was found with an arrowhead

still perforating the bone!

James Ellis: Maybe the community, made up of mostly

farmers and tradesmen, was suddenly engaged in

some kind of conflict, that forced them to take up arms.

A local grievance that escalated and turned bloody.

Narrator: The sheer size and scale of the recovered items

tells a different story.

Dr. Leonard: The more the archeologists dug around,

the more bodies and weapons they uncovered.

Experts believed the total number of dead in the valley

to be between 400 and 550.

Dr. Cantor: Based on estimated wartime fatalities

of the period, about 25% of all combatants,

that means that anywhere between

1,600 and 2,200 fighters

were involved in this one event!

That just doesn't support any scenario

of small-scale conflict between local farmers,

or even small bands of warriors.

This was an all-out conflict.

Dr. Agbedor: The data points to a complex

and multi-faceted battle.

The frontal lobe injuries indicated face-to-face fighting.

The angle and point of entry of the multiple arrowhead injuries,

reflected attacks from both short and long distances.

James Ellis: These diverse combat scenarios,

plus the high body count,

suggest a fight not amongst local civilians,

but between two organized armies of trained warriors.

If that was the case, could the Tollense River valley

be the scene of Europe's first ever battleground?

Narrator: To reveal the identities

of the two warring armies,

researchers take a closer look at the weapons

recovered from the riverbed.

Dr. Leonard: Specifically, they did a deep dive

on the arrowheads, since just like snowflakes,

it turns out no two arrowheads are identical.

The miniscule markings can reveal its age,

where it was made,

and occasionally an accurate profile of who likely used it!

Dr. Cantor: Most of the arrow- heads in the Tollense valley

had a distinctive heart-shaped appearance,

which was typical for the region.

But in addition to these 'local' weapons,

a significant number of them were from the South.

Dr. Agbedor: One wooden shaft with a socketed

bronze arrowhead, for example, was likely from

the Kingdom of Bavaria, hundreds of miles to the south.

James Ellis: While these distinctions may seem small,

the implications are potentially enormous.

The picture that emerges is an all-out battle

between a local army, and an invading one from the South.

Narrator: The discovery has the potential to reshape

our historical narrative of early European warfare.

Dr. Leonard: This is a huge deal! An organized battle

of this size, featuring bronze weapons

that were relatively new or just emerging,

not to mention the sheer scale of violence,

this was unprecedented in an area that was, until this point,

considered fairly remote and insignificant.

Dr. Cantor: What were they fighting about?

We may never know for sure.

But given the context of a rapidly growing

metalworking trade, along with skilled craftsmen,

experts now believe that this battle was primarily political,

not just territorial.

It was a fight for control of the industry.

And that's a real departure from the "rob and plunder" campaigns

that were typically associated with the era.

Narrator: The uncovered human remains,

buried deep within the Tollense riverbed,

revealed fascinating human stories of the Bronze Age,

and completely altered our understanding

of prehistoric warfare.

♪♪

Narrator: Located on the northern slope

of the Greater Caucasus Mountains,

the Republic of North Ossetia - Alania

is a region filled with scenic valleys,

deep gorges and great rivers like the Gizeldon

that cuts through the land.

Anthea Nardi: Having a diverse ecosystem,

the climate, soils and vegetation change dramatically

throughout the regions due to altitude.

Lower areas are warmer, with conditions suitable

for steppe vegetation, while higher altitudes are cooler,

leading to different plant and soil types.

As you get to the highest elevations,

there are no plants, only bare rock and ice.

Dr. Riskin: This area is sparsely populated

because it's so mountainous and it's got limited infrastructure,

but there are some [inaudible].

The small village of Dargavs has a population of just

under 200 people.

It's dwarfed by the enormous mountains next to it.

Its few dozen houses radiate out from the hillside

and down the narrow Gizeldon Valley

overlooking the [inaudible] river.

Narrator: A group of researchers and historians have come

to North Ossetia hoping to learn more about the history

of this remote area when they see something

that intrigues them all.

Dr. Agbedor: Sitting just outside the village

is a mysterious abandoned group of ninety-nine small buildings

scattered over ten miles, climbing up the side of a hill.

Almost looking medival,

the simple huts have curved rooftops,

tiny windows and come in all different shapes and sizes

with some of them being two to four stories high.

Dr. Cantor: The smaller huts have flat sides

on the front and back,

yet curve inwards and have pointed barrel vaults

or no roofs at all.

The larger huts have a pyramid vault on the inside

that holds up the roof.

The plain walls are made of stone blocks

probably mortared with limestone.

Overlooking the group of buildings

is a tall watch tower-like structure,

whose top part has been destroyed over time.

Anthea Nardi: The area is eerie and quiet,

and looks like it hasn't been inhabited for hundreds of years.

Some of the locals even believe that anyone who dares to enter,

won't return alive.

What would have caused a whole settlement's population

to just up and leave?

What is this mysterious abandoned city?

Narrator: History is filled with tales of empty towns

and villages that were once thriving communities,

but there is one other hilltop city that shares

striking similarities to the mystery settlement at Dargavs.

Dr. Agbedor: One notable ghost town in Italy is Craco,

which was famously abandoned.

It was founded by the Greeks in 540 CE.

It's perched on a hilltop 400 meters above sea level

and offers breathtaking views of the surrounding countryside.

Craco's strategic location allows for excellent visibility

over the valleys, which made it an ideal site

for defense against invaders.

Anthea Nardi: Throughout its extensive history,

Craco has navigated a series of formidable challenges.

The town withstood the ravages of the Black Plague

in the mid 1600,

successfully dismantled feudal rule,

and survived Napoleonic occupation.

Today, Craco serves primarily as a historical and cultural site,

attracting tourists, historians and filmmakers

drawn to its haunting beauty and rich history.

Dr. Agbedor: Poor agricultural conditions led to severe famine

in Crago, causing residents to leave the area.

Some heading to North America for a fresh start.

Then in the 1950s, soil conditions of the town

got worse and worse, creating landslides

that made some buildings and homes unsafe,

leading to 1800 residents leaving the town by 1963.

After that, earthquakes took their toll on the town,

and the last inhabitants were forced to abandon

this once flourishing community.

Narrator: So could a natural disaster have forced the people

to abandon the site near Dargavs?

Dr. Riskin: It's possible, but there's no evidence to suggest

that any great catastrophe ever took place.

All of the buildings are pretty much intact,

and there are no historical records of a natural disaster

ever affecting Dargvas badly enough

to cause people to abandon their homes.

Narrator: With the possibility of a natural disaster ruled out,

the team starts to look through the tiny houses

and are shocked with what they discover.

Dr. Cantor: All of the huts in Dargvas

are filled with human bones!

The bones and remains of over 10,000 people,

some that even still have their flesh attached.

Many of the corpses are fully clothed and have jewelry

and belongings with them.

This abandoned settlement isn't a settlement at all,

it's a series of crypts for the dead.

Anthea Nardi: The architecture now makes more sense as well,

as the square window openings were used

to put the bodies inside the tombs

and were usually in higher positions

to prevent looters or animals from disturbing the remains.

The taller the building, the greater the number of people

who were buried inside and some even have underground chambers.

The watchtower that overlooks the huts

is also there for a purpose,

it's there to watch over all of the resting souls.

Dr. Cantor: We see a few different burial practices here.

For example, some of the remains are buried in coffin

shaped like boats.

And one even has an [inaudible] next to it.

Many ancient cultures believe that the dead would have to

cross a river to get into heaven.

So maybe that's what we're seeing here.

Narrator: After uncovering the vast bone collection in Dargvas,

the team now turns their attention

to another burial site,

renowned worldwide for its impressive assembly

of human remains.

Anthea Nardi: The catacombs of Paris are an example

of a similar burial practice,

but to a much larger extent with some interesting differences.

Located about 65 feet beneath Paris,

the catacombs extend for miles,

and have over 6 million people buried there.

Dr. Agbedor: The walls are covered in skulls, femurs,

and other bones stacked in interesting artistic formations

while other areas feature engraved plaques

with poetic inscriptions,

creating a somber, church-like atmosphere.

Dr. Cantor: The catacombs were created back in the 18th century

when Parisian cemeteries were overflowing with the dead,

which led to health concerns as decaying remains

contaminated nearby water supplies.

In response to both, this and the growing number of sinkholes

that were plaguing the city,

a department was created tasked with stabilizing and reinforcing

these underground tunnels

that got turned into catacombs for the dead.

Dr. Riskin: The need for the Paris catacombs was rooted

in something that happened hundreds of years before.

The bubonic plague,

which generated a massive number of bodies

in the crowded conditions of Paris.

It's been estimated that half of that city's population,

which was around 100,000 people at the time,

died and they got buried in all the different cemeteries.

But those all started to burst at the seams.

So could the crypts at Dargvas have some connection

to a disease as well?

Narrator: The tombs of Dargavs date back to the 16th century,

and historical records indicate that a devastating plague

was starting to severely impact the region.

Dr. Cantor: The plague that struck Ossetia

killed tens of thousands and reduced the Ossetian population

from 200,000 at the end of the 18th century,

to just 16,000 by the mid-19th century.

Dr. Riskin: According to oral history,

some of the structures ar Dargavs were built

as quarantine shelters

where people infected with illness

would isolate themselves to prevent spreading the disease.

Villagers would deliver food and supplies

until the sick eventually died in those structures.

And once they did die,

the remains would just decompose there,

creating this haunting legacy

that's been passed down through generations.

Narrator: While the plague is believed to be

one of the reasons for the creation of the mausoleum site

at Dargavs, it was not the only motivation.

Dr. Riskin: The crypts were also built to house

multiple generations of the same family.

Each crypt served as a family tomb,

where the remains of different family relatives

would be placed over time.

The family vaults reflect the strong kinship ties

in that community and the importance of familial heritage

in the Ossetian culture.

Dr. Agbedor: In ancient Ossetian culture

death was not seen as a final separation from the family,

but rather as a transition to another realm.

People were buried with personal belongings

like jewelry and clothing,

signifying a belief in an afterlife

where the deceased might still need their material possessions.

Dr. Cantor: The size of each crypt was often reflective

of the family's social status as well.

Larger, more ornate crypts were reserved

for more affluent families,

indicating that wealth and prestige were passed down

through generations, along with burial practices.

Anthea Nardi: Many historians believed

that the tombs were constructed not only as burial sites

but also as a response to the challenging geography

and resource constraints in Ossetia.

The area's mountainous terrain made it difficult to sustain

large farming regions, and land was so limited

that every inch had to be carefully managed.

This scarcity likely influenced the use of these unique,

multi-level crypts, where families could bury

multiple generations within confined spaces,

reducing the need for sprawling cemeteries

that would further encroach on farmable land.

Narrator: The story of Dargavs has become a haunting look back

at the history of the region.

The questions that still remain only add to the mystery

of the area which is now known as The "City of the Dead".

♪♪

Narrator: Set in the Rocky Mountains

of southeastern British Columbia,

Marble Canyon is a stunning natural feature

in Kootenay National Park,

renowned for its dramatic landscape

and unique geological formations.

Anthea Nardi: The area is characterized by steep

weathered peaks and towering walls made of limestone

that give the appearance of a crumbling castle wall.

The canyon offers breathtaking views of large forested valleys,

colour-splashed mineral pools,

and unique marbleized colours

that have slowly worn away from centuries of rushing waters.

Dr. Agbedor: The winters here can be stunning,

as the rugged landscape gets covered in crisp,

white snow creating a winter wonderland.

December typically sees the heaviest snowfall,

averaging up to 43 inches.

Temperatures in the winter months vary due to elevation.

But the lowest temperature averages at around

five degrees Fahrenheit.

♪♪

Dr. Riskin: The Burgess Shale is a fossil bearing deposit

that's been exposed in that area.

That site was first discovered in 1909,

and it has been providing unbelievable

paleontological wonders ever since.

The rock unit is a black shale.

It crops out in a bunch of different locations,

like Yoho National Park, Kicking Horse Pass,

and a new recently discovered area

in Kootenay National Park.

Narrator: A group of scientists are on a research expedition

at the Burgess Shale

when they discover something unusual.

A. Nardi: In an area that would have been an ancient ocean,

they find a strange fossil,

thin, cylidrical and almost tubular in shape,

that's built in the rock sediment,

and only about an inch long.

The rock features several narrow tubes on its surface,

which are marked by elongated depressions.

James Ellis: The marks on the rock surfuce

almost look smudged and hard to identify,

but must belong to some sort of ancient creature,

that would have been buried by underwater mudslides,

that packed it in silt while sweeping its body down,

into an oxygen-poor environment, deep in the ocean.

The mud and low oxygen allowed the specimen to be preserved.

Dr. Riskin: There's no visible vertebral column or limbs,

or other features you would see in animals today.

It almost looks like it's branching more than anything,

so it's really hard to decipher exactly what this thing is.

What ancient creature left this weird fossil?

Narrator: The team uses a combination of stratigraphy

and radiometric dating to determine the age of the fossil

and are shocked with what they learn.

Dr. Agbedor: It's 505 million years old,

which means, it's part of the Cambrian period,

which is a period that produced the most remarkable

surge of evolution in Earth's history.

The Cambrian Explosion gave rise

to an extraordinary diversity of life,

including many of the major animal groups

that are still around today.

James Ellis: The exact cause of this

biological explosion remains unknown.

It may have been triggered by Earth becoming more hospitable,

with a warming climate and rising sea levels

flooding lower areas to create shallow marine habitats,

which would be ideal for the emergence of new life forms.

Maybe, lifeforms like the one found in this fossil?

Dr. Riskin: None of the creatures that are alive today

were around at the time of the Cambrian Explosion,

but a few of the lineages we do have today

can be traced back to that time.

For example, brachiopods, which kind of look like clams,

but they're not really clams.

And the first arthropods, and their descendants

include things like insects and spiders and crustaceans.

Narrator: The shape, size, and time period

are enough to give the team enough information to think

they might know what this tubular fossil could be.

Anthea Nardi: One sea creature that first appeared

in the Cambrian period was coral.

As we know, coral is a marine invertebrate

that lives in colonies and builds

hard rock-like structures in the ocean.

Each coral polyp is a small, soft bodied organism,

that secretes a hard calcium carbonate skeleton,

which over time, builds up to form coral reefs.

These reefs are not only beautiful places to snorkel,

but they provide the ecosystem

which sustains many sea creatures.

Dr. Riskin: One of the most important marine groups today

is the corals.

They form the ecological and physical foundation

of marine ecosystems.

They're crucial for sponges and oysters and mollusks

and crustaceans, and all kinds of different fishes.

And although those corals cover less than 1% of the ocean floor,

they provide critical food, shelter and breeding grounds

for a ton of different organisms.

J. Ellis: When coral fossilizes, it takes on a tubular shape

similar to those found in the Burgess Shale.

Coral species with branching growth patterns,

such as rugose or tabulate corals often display a tubular,

or horn-like appearance in their fossilized forms.

But the closest form of coral in the Burgess Shale

is a creature called a Cnidaria,

the precursor to modern corals and jellyfish.

Though there can be examples of tubular corals found here,

none have been 100% confirmed.

Narrator: With the realization it might not be coral after all,

the researchers open their eyes

to other possibilities of marine life.

Dr. Agbedor: Algae or seaweed would have been all over

the marine floor, so this could very well be a type of algae

or seaweed, that left an impression on the rock.

Many fossilized algae have been found over the years,

that closely resemble this mysterious discovery.

Anthea Nardi: In China, microfossils of green seaweeds

estimated to be one billion years old were discovered,

potentially linking them to the earliest land plants and trees

that emerged around 450 million years ago.

The algae, known as Proterocladus antiquus,

were found imprinted in rock from an area

that was once an ocean, but is now dry land.

♪♪

Dr. Riskin: Some algae that closely resemble these markings

include Yuknessia simplex, which was discovered in Utah.

That type of alga features these long branches

extending from a short, wide hollow stem.

That represents an early form that ultimately contributed

to the evolution of modern land plants.

Narrator: Deciding this is the most logical conclusion,

the team concludes that the fossil must be a form of algae,

and gives it the name Margaretia Dorus

and puts the matter to bed for years.

But a new discovery changes everything.

James Ellis: Several new fossilized remains

of an ancient worm called Oesia,

are discovered in the Burgess Shale.

Where the early fossils of the Oesia were not as clear,

the new samples are much clearer and better preserved.

Anthea Nardi: The new fossils offer researchers

unprecedented insights into the internal anatomy of Oesia,

revealing that they measured around 2 inches in length

and almost half an inch in width.

The front end of these animals is shaped like an acorn,

hence the name.

The acorn consists of a muscular proboscis

and a collar that may be used to burrow into soft sand or mud.

Though it is not related to earthworms or parasitic worms,

Oesia belongs to a group known as hemichordates,

which are more closely related to sea urchins and starfish.

Narrator: As the team finds an abundance

of these ancient worms, they also find more examples

of Margaretia Dorus and realize they might be connected.

James Ellis: Inside the new Margaretia fossils,

the researchers actually found remnants of the Oesia,

as many fossils were cracked along the axis of the tube,

revealing the Oesia inside.

This means Margaretia was not a random seaweed,

but rather the home for these ancient little worms.

Dr. Agbedor: The tube structures were generally larger

than the Oesia worms,

with some homes measuring up to 20 inches in height.

They were probably composed of collagen

and protected the worms from predators.

Most likely, the Oesia had a gland that produced

strands of collagen, like a spider with a web,

and could be "knitted" into the tube structure,

leaving "windows" for water to pass through,

so that the worms could feed.

The fossils only showed one worm per tube structure,

which means, they lived a very lonely life.

Anthea Nardi: Looking back at the original fossil specimen,

it does in fact have a worm present,

but it's so badly decayed, it looks like

a dark line of reflective carbon.

This is what led to the original misinterpretation

of what it was.

Dr. Riskin: The really interesting part is that Oesia

is actually a primitive hemichordate,

that is a group that belongs to a larger group

called the Deuterosomes, and that makes it

an ancestor of everything with a spinal column,

including you and me, which means that

our ancestors were penis-looking things that lived in tubes.

By looking at all of these obscure and strange

ancient groups, what researchers are really trying to figure out

is where we came from,

what our ancestors looked like,

when we are so far back,

that we share a relationship

with all these weird worms.

Narrator: These tiny creatures and their tubular homes

might help connect humans to their most basic ancestors,

giving us all a better understanding

of where we came from.

♪♪