Original subtitles

NARRATOR: Destruction of biblical proportions

prompts archaeologists to uncover its origin.

- They discover human remains. These bodies are extremely mangled.

NARRATOR: A massive storm uncovers new secrets in Teotihuacan.

- They could see that it was clearly a tunnel,

but it was blocked off at both ends by these giant boulders.

- But why? What are these boulders guarding?

NARRATOR: A landslide in southern England

reveals an ancient cave.

- It remained hidden for a long time.

- Despite its size, could someone have been living in it?

NARRATOR: All over the world,

incredible discoveries are being revealed

by devastating events: floods,

earthquakes,

droughts, hurricanes, volcanic eruptions.

Trails of destruction expose long-lost mysteries.

This is Discovered by Disaster.

One of the most well known stories in the Christian Bible

is that of the destruction of the city of Sodom.

The book of Genesis reads that

"the Lord rained uponSodom brimstone and fire

from the Lord out of heaven, and he overthrew those cities,

all the plain, and all the inhabitants of the cities,

and that which grew upon the ground."

- The story is a disaster of unbelievable proportions.

The whole city of Sodom and every living thing in it

was obliterated, wiped off the map.

And it wasn’t just the city itself, but the entire area

that was left uninhabitable. The earth was made barren,

unable to be cultivated.

- When we talk of written sources from the ancient world,

most of what was written down originated in the oral tradition,

in stories passed on through generations.

So some stories in the Bible may have some grounding

in historical events, but by the time they were written down

they had taken on an entirely different character and meaning.

- Today, over 2,000 years since much of the Bible was written,

it's difficult to say what information in it

is grounded in truth, versus hat is entirely fiction.

Which raises the question,

could the existence and destruction of Sodom have been true?

NARRATOR: Determined to find out, an archaeologist investigates.

He first looks at the ancient sources:

chapter 13 of the Book of Genesis mentions that Sodom was located

east of the River Jordan and northeast of the Dead Sea.

- So the book of Genesis points us

to exactly where an ancient Jordanian city,

Tall el-Hamam, is located.

This city was initially established over 6,000 years ago

and saw continuous human occupation up until the early Roman period.

- The site was discovered a few decades ago.

Previous excavations have revealed that it’s essentially

a fortified urban centre, 2,000 ft wide, over 3,000 ft long.

It's divided into an upper and lower section,

with the upper section being 115 ft higher than the lower.

In the fort’s grounds was a palace four to five storeys high,

constructed mostly of mudbricks. - The palace isn’t five storeys

today, but we can still see the layers of rubble

from the different floors that have collapsed.

But the weird thing is, despite the entire thing

having been made of mudbrick, there are no intact mudbricks

from the upper floors found in the rubble.

They’ve just vanished. NARRATOR: Archaeologists

do eventually find remains of mudbricks

in the excavation layers, but they are completely shattered,

basically just tiny fragments of what they once were.

- What's also strange is that the sediment

in which these remains are lying shows no sign

of having been exposed to erosion, either by wind or water.

This means that a natural process taking place

over the course of thousands of years

can’t have destroyed the mudbricks.

So how have these mudbricks been pulverised?

NARRATOR: The archaeologists also discover ash,

charcoal and other charred organic material

among the pulverised mudbricks.

- So there must’ve been a catastrophic fire here

that caused a large amount of damage.

It would definitely have contributed to the collapse of this palace,

but how and why this fire started is impossible to know.

My best guess would be either an act of war,

or an uncontrollable fire that broke out

before or after the city had been abandoned.

- Radiocarbon dating of these organic materials

does give us at least one definite fact to work with:

it shows that they were burned somewhere around 1650 BCE,

placing us in what's known as the Middle Bronze Age.

- The Middle Bronze Age in the Jordan Valley

was a time that saw increased urbanisation

and population growth.

It's believed around 50,000 people lived in the area,

so for the time, it would have been a busy place.

- With all those people, it's possible that some horrific war

could have taken place, one where a city,

or several cities were destroyed.

So maybe the story told in Genesis, that of the raining of fire

onto the city, was actually done by humans.

NARRATOR: Exploring the site further,

the team makes a shocking discovery

among the mudbrick, ash and charcoal remnants.

- They discover human remains, and not just any human remains:

these bodies are extremely mangled.

On one of them, you can see evidence of charring

on the femurs. The toes are in a hyper-flexed position,

which is what we often see when a body has been exposed

to high temperatures either at or after the time of death.

Some of the bones have even been splattered with melted glass.

So the fire that burned here was exceptionally hot.

- One of the bodies is in a grotesque position.

Its legs are hyper-flexed backwards,

and its knee joints are disarticulated,

meaning detached from the body.

And then finally, one skeleton is in a crouching position,

with its hands protecting its face. It looks like

this person shielded him/herself from the fire.

- But there are no markings on the bones

that could have been the result of blades, projectiles,

or even a blunt force. In other words,

these aren’t the victims of a battle or any form of violence.

- Also, there isn't any evidence of them

having been afforded a proper burial.

So when they were killed, they lay where they had fallen,

with no-one taking the time to bury them.

These remains and their postures actually remind me

of the victims of the volcanic eruption

outside the ancient Roman city of Pompeii.

- Well, there is a volcano field pretty close by:

it’s called Harrat al-Shaam,

and is situated about 140 miles from Tell el-Hamam.

But the last time it erupted was in 2670 BCE,

1,000-plus years before these people were killed.

NARRATOR: As the excavations continue, among more debris of ash

and charcoal, archaeologists find pottery shards

lying only 50 feet from the palace grounds.

- Almost all of the pottery has shattered

into two to three-inch pieces. What must be the inner side

is smooth to the touch and uniform in colour,

but the reverse side tells a completely different story.

Here, the shards are discoloured, rougher in texture

and have a lot of little pockets in them.

- These little pockets are what we would call vesicular,

basically a volcanic rock texture

which is characterised by a lot of cavities.

That occurs when magma, or molten rock, cools.

When it does, it releases gases,

which then create this rough texture we see on the pottery shards.

So these shards have basically melted, at least partially.

But what can create enough heat to do that?

NARRATOR: In order to ensure

the pottery is contemporary to the human remains,

the shards are radiocarbon-dated.

- The pottery is also dated to the Middle Bronze Age.

So the destruction of the pottery probably happened at the same time

as the death of these individuals discovered nearby.

- They also discover that the pottery

appears to have been exposed to temperatures greater than 2800 F,

maybe as high as 4500 degrees.

That is really hot, considering that magma

is generally only around 1800 to 2200 F.

So what could possibly burn this hot?

NARRATOR: Investigating the site further, the team makes

its strangest discovery yet. - There is melted roofing clay

with ghostly imprints. Truly bizarre.

So what could've caused that?

- In 1650 BCE, most inhabitants of this region

built their roofs out of clay, straw, plant stems and leaves.

These shapes that we see on the clay

are the result of this extremely intense heat

instantly vapourising the water and carbon inside the plants,

and then fusing what was left of the plant into the clay.

You would think only something like a nuclear explosion,

or the sun itself would be able to do this.

- Obviously, it wasn’t a nuclear explosion,

so it would have to be something extraterrestrial,

something that has the power of one or several nucear bombs.

So perhaps it was an asteroid.

NARRATOR: Asteroids have left many a mark on the planet Earth,

from the famous Chicxulub extinction event,

where a six-to-nine-mile large asteroid hit today's Mexico

and exterminated the dinosaurs, to far smaller ones

like the one that hit Tunguska, Siberia in 1908.

- By no means was this Tunguska asteroid

anywhere near an extinction level event.

The asteroid measured only around 130 feet across,

and exploded six miles above the Earth.

Even so, people more than 20 miles away

reported seeing a flash brighter than the sun

before they were blown into the air and knocked unconscious.

- Because the asteroid exploded before it hit Earth,

there's no impact crater at Tunguska.

So could it be that something similar happened

at Tell el-Hammam? - It could be.

There is no impact crater at Tell el-Hammam.

But, like at Tunguska, if the asteroid blew up

while still in the air, we would expect to find microscopic evidence.

NARRATOR: Shocked quartz are tiny, fractured grains of sand

that can only form when under immense pressure.

It has been discovered at other impact sites

across the globe, and is taken as proof

that an asteroid either exploded above or smashed into the Earth.

- 'Immense pressure' doesn't really do it justice.

In order for shocked quartz to form,

each grain of sand has to be placed

under 725,000 lbs per square inch of pressure.

To put that into perspective,

an empty jumbo jet weighs roughly 400,000 lbs,

so try to imagine almost twice that weight

on top of your little toe.

NARRATOR: To test the theory,

the achaeologists take samples of the sedimentary layer

where a lot of the discoveries were made,

and extract quartz grains, which they observe

under a microscope.

- What they see is that the quartz’s microscopic structure

is different from normal quartz.

There are these parallel lines in the grain,

basically little fractures, exactly what characterises shocked quartz.

- It's likely that on that fateful day in 1650 BCE,

an asteroid appeared over Tell el-Hammam

and caused what we can only imagine

as an apocalyptic, Biblical level of destruction.

The event may then have been memorialised in oral histories,

passed on and likely embellished from generation to generation.

- But if this is where the Biblical story of the city of Sodom was born,

and that's a very big if, there should also be evidence

that the site was largely abandoned following this catastrophe.

NARRATOR: When arriving at the excavation site

every morning, archaeologists notice that a white crust

formed on the destruction layer overnight.

- This is the layer containing the evidence

we have been looking at so far. So what happens is

the nightly drop in temperature creates humidity under the surface,

which in turn pushes minerals to the top.

This white crust is actually salt.

- Measurements show that the excavation layer from 1650BCE

has a remakably high salt concentration.

It's more than four times higher than in the older or younger layers.

- You know the expression 'salting the earth?'

This is the idea that a conqueror of a city or state

would sow the earth with salt to prevent anything

from ever being cultivated again, as salt poisons the soil.

Basically, this meant that the defeated population

would never be able to rise against their conquerors again.

- The average salt content of the destruction layer

ranges upwards from 4%. This is very, very high.

Wheat, for example, a staple crop in the Middle Bronze Age,

won’t even grow in soil that has a salinity of over1.8%.

So where did all this salt come from?

- Well, the Dead Sea is right next door,

and it has a salinity level

almost ten times higher than normal seawater.

So when the asteroid exploded

and unleashed these incredibly high velocity winds and temperatures,

the water in the Dead Sea was vapourised.

The salt crystals dispersed across the land,

poisoning it for centuries to come.

NARRATOR: Previous archaeological studies have shown

that the region was unoccupied for 600 years

following this extra-terrestrial event,

but the reason was never determined.

- So perhaps we now have some answers.

Although it's unlikely anyone in Tell el-Hammam

survived the actual event,

the cataclysm would have been remembered

by those in the region who heard about it,

or saw itsimpact.

- This memory was then passed down from father to son,

mother to daughter. With the passage of time

and in light of our human need to ascribe meaning to tragedy,

it transformed into a story about the God of the Hebrew Bible

raining hellfire down upon the people of Sodom.

It’s possible. We'll likely never really know.

NARRATOR: More recent and up to date analysis

of the available mineralogical and geological evidence

has cast doubt over whether or not

an asteroid really did explode over the city of Tell el-Hammam.

The only thing that is certain

is that stranger things have happened,

and it isn’t a stretch to imagine that the Biblical story of Sodom

has some grounding in such a horrific event.

NARRATOR: In the fall of 2003, an unprecedented rainstorm

appeared over the ancient Mesoamerican city of Teotihuacan.

The deluge flooded the city’s magnificent avenues,

washed away its courtyards, and turned the entire area

into a river of mud and debris.

As a result, archaeologists conducting excavations

at one of Mexico’s most famous sites had to halt their work.

- At the foot of one of the city’s main temples,

The Temple of the Plumed Serpent,

the downpour destabilised the ground to such an extent

that it collapsed on itself. It was absolute mayhem.

- But as chance would have it, the first to spot this

was a Mexican archaeologist. The collapse was located

in the southeast section of the temple,

and as he approached the area, he noticed the sudden appearance

of a three foot-wide sinkhole. NARRATOR: The archaeologist

who peered into the underground, could only see darkness.

Resolving that it was worth an investigation,

he lowered himself into the unknown.

- So when they finally got underground and lit that space,

they could see that it was clearly a tunnel

that led towards the Temple of the Plumed Serpent.

But it was blocked off at both ends by these giant boulders.

- These are absolutely huge stones, so whoever placed them here

intended this tunnel to remain impassible,

and for whatever lies beyond it to remain a secret.

But why? What are these boulders guarding?

- This is a pretty astonishing find,

because not only is Teotihuacan one of the biggest

and most magnificent pre-Columbian cities that exist,

it is also one of the least understood.

- We don’t even know what these people called themselves,

'Teotihuacan' is actually an Aztec word

meaning 'the place where men become gods.'

The city was long abandoned by the time the Aztecs saw it

in the 1300s, but even so, it's clear

that the Aztecs were equally, if not more fascinated with Teotihuacan

than we are.

NARRATOR: Archaeological excavations and analysis

has determined that the site of Teotihuacan

was occupied from as early as 400 BCE,

reaching its peak in power and population 900 years later,

when 200,000 residents are thought to have called the city home.

Its golden years didn’t last long, however,

as the civilsation collapsed and the city was abandoned

sometime between the early seventh to mid-eighth century.

- So this would have been a decent-sized city even today,

let alone 1500 years ago,

and the architects who designed it put a lot of thought into it.

It's built on a north-south axis,

with the most important temples located along this orientation.

These buildings are connected by the Avenue of the Dead.

- The Temple of the Plumed Serpent is found in this courtyard

known as Ciudadela. whereas the city’s largest temple,

The Temple of the Sun, is located a little further north

along the Avenue of the Dead.

- A tunnel was found underneath this temple,

but unfortunately looters had gotten to it

in the intervening thousand years, so it remains a mystery.

But maybe it had a similar purpose to this one?

- It could potentially provide a lot of much needed information.

We still don’t know who the people who built this city were,

nor do we know that much about

their cultural, social, political processes.

The little we do know is that they practised human sacrifice

and worshipped gods similar to those the Aztecs revered

some 700 years later.

NARRATOR: Using ground-penetrating radar,

the archaelogist and his team scanned the entire Ciudadela,

hoping that they would be able to see where the tunnel began,

and where it ended. - This technolgy is incredible.

It basically allows us to take an x-ray of the ground

so we can see what's beneath the surface

without having to dig. And this GPR scan

shows that the tunnel was actually around 330 feet long,

and had a starting point in the Ciudedella

that led directly under the Temple of the Plumed Serpent.

NARRATOR: With a clear picture as to the extent of the tunnel,

the archaeological team begins painstakingly slow excavations,

at times removing soil with a toothbrush

to prevent damaging any potential artefacts.

- 50ft into the tunnel is a recess carved into the wall.

And there in the half-dark,

there's this astonishing sight of the walls

sparkling with little bursts of light.

It's almost like stars at night.

- In the walls are small pieces of brassy metallic mineral.

It's pretty brittle and reminds you a little of gold

the way it's gleaming. It's definitely not gold,

but it is what we call fool's gold or pyrite.

- And at the end of the tunnel, there are several small pools

containing a silvery white liquid. It has a really cool texture.

Even though it's liquid, it doesn't mix or cling to anything.

So it's pretty obvious what this is: it's mercury.

- Seeing all this in low lighting does remind one

of looking into the night sky, into the universe.

These little silvery pools made of mercury

have been found in other archaelogical sites in Mesoamerica.

They're meant to symbolise water, lakes in the underworld,

which people at this time thought of as a watery, dark place.

So perhaps the mercury pools represent this aquatic character,

and the enclave is meant as a recreation of this underworld.

NARRATOR: In other Mesoamerican cultures,

like that of the ancient Maya, caves were gateways to the underworld,

not in the sense of a place of punishment

reserved for the wicked, but rather it was home to a variety of gods

related to death and sickness.

- We don't know.

But it could be that the people of Teotihuacan had similar beliefs,

and so they constructed this tunnel as some kind of a ritual space.

Or maybe it functioned as a cemetery.

- What we do know is that for the people of Teotihuacan,

the realm of the underworld wasn't just where life ended,

but it was also where life began. So it had a dual significance.

NARRATOR: In the approach to the enclave,

archaeologists discovered several wood fragments nestled in the soil.

When the wood is cleaned, it gives off a red pigment

along with sediment.

- In order to find out what this red pigment is,

something called X-ray fluorescence is used.

This is a form of analysis that identifies

what elements make up any given artifact or material.

- The XRF analysis shows that the pigment

contains the elements that make up a material

that was extremely valued by the ancient cultures

of Mesoamerica. It's cinnabar.

Its vibrant red colour represented the blood

and the heat of life.

So it was primarily used on cherished or ceremonial objects.

NARRATOR: As excavations continue, the archaelogists

find many fragments of a statue that has broken down over time.

All the pieces are put back together,

revealing a familiar likeness.

- These googly eyes, fangs

and the blood running from his mouth identify him as Tlaloc,

a god associated with water and fertility,

as well as fire and lightning.

- As the storm god, he was the guardian of or the owner of

the underworld's sacred waters.

We know this because he was worshipped by the Aztecs

hundreds of years after the collapse of Teotihuacan.

So it's likely he meant something similar to those people.

All of this supports the hypothesis

that this tunnel had some kind of ceremonial role

dedicated to the gods of the underworld.

NARRATOR: Radiocarbon dating of coal found inside the tunnel

informs archaelogists that it was built

sometime between 1 and 100 CE,

and closed for good around 220 CE.

- Previous research has shown

that the Temple of the Plumed Serpent

was built around the time of the tunnel's closure.

This is interesting, because it would mean

that whatever the people of Teotihuacan's intent was

for the tunnel, it must have been extremely important,

because it came before the construction

of other majorly significant buildings.

NARRATOR: In order to fully excavate the tunnel,

the archaelogical team employs two robots

to dig through the soil. When the robots

are directly under the Temple of the Plumed Serpent,

they come to a cross-shaped chamber piled high with many offerings.

- Among the treasures are four statues

made out of greenstone, wearing garments and beads,

with their eyes wide open. Incredibly,

some 2000 years after being left there,

two of them are still in their original positions,

leaning back and gazing upwards.

- The citizens of Teotihuacan believed that the universe

had three distinct levels: the celestial plane,

the earthly plane, and the plane of creation,

which was also the underworld.

- So these two statues are peering upwards into space

towards where these three planes meet.

That's why it's thought that they are

the founding shamans of Teotihuacan,

who brought the people to this sacred place where civilisation

could be born, and life could begin.

NARRATOR: Over several years of excavation,

archaelogists discovered 75,000 different artefacts.

Yet no grave or burial deposit was found in the tunnel.

- So the tunnel wasn't used as a place

to bury aristocrats or royalty.

Rather, it was used as a place where the priests of Teotihuacan

could leave offerings to appease their gods.

- And they didn't just leave these offerings anywhere:

they left them in a special place

that served as a recreation of the underworld.

NARRATOR: Archeological excavations

are ongoing at the city of Teotihuacan,

making it one of the sites

with the longest history of exploration in Mexico.

With time, more of its secrets will be uncovered,

and more of its questions might be answered.

Until then, the city and its temples

preside over one of the most ancient mysteries of the Americas.

NARRATOR: The British Isles are notoriously wet,

but during the winter of 2020,

endless rain triggered flooding across parts of southern England.

- The River Wey is a tributary of England's famous River Thames,

and is known to frequently flood. The water spilling over its banks

caused damage to homes and businesses

and disrupted vital infrastructure. - These floods don't only

destroy manmade structures: they also trigger a lot of erosion

and even landslides.

In St Catherine's Hill, overlooking the River Wey,

an entire section of the hill that leads down into a railway cut

collapsed, blocking the line.

NARRATOR: With an important railway line rendered impassable,

engineers and railway workers were called in to clear the tracks.

What they found when they arrived was more than they'd bargained for.

- 20 feet from the top of the hill, above the rail tracks,

they could see a little sandstone enclave

into which strange shapes had been carved.

- The enclave itself looks quite natural.

There are no tool marks on the side of the walls

that would indicate it had been dug out. It's basically

just an old cave that's remained hidden for a very long time.

- But there are several little pockets

cut into soft sandstone.

These have been made by human hands.

So perhaps this was used as some form of shelter?

- But it isn't very big.

It's only 5.5ft high and 6.5ft deep.

So only one or two people can fit in there comfortably.

That said, because sandstone is porous

it's quite vulnerable to erosion and disintegration.

So we can't discount the fact that it may have been bigger

at one point and able to accommodate more people.

NARRATOR: Owing to the strange pockets

carved into the sandstone wall,

work on clearing the railway was immediately brought to a halt,

and archaelogists called to the scene.

Upon examination, they notice that the cave ceiling

is stained black and that many of the little niches

also contain streaks of a similar colour.

- There are also two little pits in the floor stained black,

like the ceiling and the pockets in the wall.

And if you drag your finger across that black,

it leaves a stain on your finger.

- So this must be soot.

The little pits we see must have been dug out for fire,

and people may have placed candles or torches in the little niches.

But for all this soot to have built up in the ceiling,

this cave must have been in use for a prolonged period of time.

Despite its size, could someone have been living in it?

- It's possible. But even going back to Stone Age Britain,

people for the most part lived in temporary or permanent structures

made out of wood and skins and other organic materials.

Caves would likely have been used for shelter at times,

but not to actually live in. NARRATOR: Archeologists spot

a two-foot high, somewhat triangular shape

carved into the cave wall. Within this shape

there are several other similarly shaped recesses.

The outline of an arch encircles these carvings,

followed by a few circular impressions

tracing the arch's outline.

- This is what is known as a Gothic arch,

and these little recess pits outlining it

are likely imitations of the wedge-shaped stones

used to construct the arch. - This style of architecture

wasn't used until long after Christianity had come to England.

It's typical of the style of architecture

seen from the mid -12th to the 16th century CE.

So whatever this cave was for,

it was used by people in medieval England.

NARRATOR: Probing the area further,

the archaelogists notice that right next to the Gothic arch

is a cross with a line going across the bottom of it,

and a faint semicircle below.

- This line at the bottom indicates that it's a Calvary cross.

In the Christian faith, there are several types of crosses.

You have, for example, the Maltese and the Greek Orthodox ones,

both quite different from the one we see here.

- The semicircle below it symbolises Golgotha,

the hill outside Jerusalem upon which Christ was crucified.

It's pretty safe to say the cave performed a religious function.

NARRATOR: Old maps show that long before the hill

was given the name St Catherine's Hill,

it was in fact called Drakehull,

meaning the Hill of the Dragon in old English.

- You can often learn a lot about a place

from its name or what it was called in the past.

Place names reflect a bunch of different things,

like events that have taken place, or even

the location's cultural or spiritual significance.

- According to old English folklore,

it was believed that dragons lived in caves,

where they often guarded a fantastic treasure. So could it be

that the cave and its use are rooted a pre-Christian religious tradition.

NARRATOR: At the top of the hill, above the cave,

are the ruins of a 14th century chapel

called the Chapel of St Catherine.

- As its name indicates, this chapel was dedicated

to Saint Catherine of Alexandria.

According to the stories, she was martyred by a Roman emperor

for refusing to honour Roman gods.

In other words, she opposed pagan idolatry.

- So it seems like Drakehull,

or St Catherine's Hill as it's now called,

had this long-established importance

to the people of pre-Christian England, and that

after the establishment of Christianity,

its significance remains, even though the symbolism

and spiritual practices that happened there were changed.

- It was commonplace for Christianity

to appropriate sites, dates

and stories sacred to pagan religions. And why?

Because it ensured a smoother transition

from being a non-believer to deciding to convert.

For example, the winter solstice, darkest day of the year,

an important pagan celebration, also coincides,

and this is no coincidence, with Christmas.

- So when they built this chapel on top of the hill

to reassert their Christian ideology,

they dedicated it to Saint Catherine of Alexandria

because, after all, she was killed

for refusing to acknowledge pagan gods.

But regardless of whether you were a Christian or pagan,

why did the hll have a mythical or religious significance

in the first place? NARRATOR: At the base of the hill,

there was a freshwater spring, used since ancient times.

- Not only is this hill a prominent feature

of the landscape but a source of freshwater.

We know that springs often took on a sacred meaning

for the people of pre-Christian as well as medieval England.

Chapels and ritual spaces were often built

near or over these sacred places.

So it could be why we see a place of worship inside a cave.

- OK, so you've got this chapel in this cave

situated in what looks to have been an historically important place

for the people in that region.

But part of this significance only appears

when you step back and look at the big picture.

You have to think about where this place is

in relation to other important religious centres.

NARRATOR: St Catherine's Hill is situated

a little over halfway between the cathedrals at Canterbury

and Winchester, two of the most important places of worship

in medieval England. - Pilgrims would follow

the Pilgrims' Way to get between these two places.

In fact, you can still walk this same path today.

- It could be that St Catherine's Hill,

with its chapel and natural spring, was a good place to rest and pray

on this roughly 125-mile journey.

The cave could have provided a quiet place

for contemplation and prayer for weary pilgrims.

- But it's cool to think about how a place's significance

changes as the times change.

The ancestors of those medieval pilgrims

may well have stopped at the exact same place

for pretty much the same reasons, but they would have been worshipping

a different god, or different gods.

NARRATOR: The cave sits as a testament

to the fact that over time humans don't really change,

but culture and tradition does.

It could be that many years from now

people will be seeking spiritual comfort at St Catherine's Hill,

but doing so in a manner or to a god that is foreign to us.

In the summer of 2022,

Europe experienced one of its worst droughts in 500 years.

For two months, no serious amounts of rain fell across the western,

central and southern regions of the continent.

As the intense heat drained rivers and reservoirs,

the gravity of the situation became clear.

- Major rivers were running dangerously low.

In France, the Loire was so low it could be crossed on foot

in some places. And the Rhine, one of the longest rivers

on the continent, was no longer able to accommodate barges.

- For hundreds of years, if not more.

the Rhine has been the lifeblood of the European economy.

Flowing through six countries,

it has facilitated trade and travel for centuries.

- Germany, which is Europe's largest economy,

uses the river for 80% of its inland shipping of goods,

and this includes oil and gas.

As a result of the lack of cheap and effective transport,

the German economy, fourth biggest in the world, shrank.

But how does a drought lead to a contraction in the economy?

- Because the rivers were running dry,

France had to reduce the energy output

of their nuclear facilities because they didn't have

enough water to cool their reactors.

NARRATOR: Apart from the impact to the transport networks,

agricultural production declined, and thousands of people died

as a result of the heat. And as the situation worsened,

the rivers just kept getting lower and lower.

The Elbe was no different: in summer of 2022,

the river's normal levels were down by several feet,

and along its banks in the Czech town of Decín

the lower water levels revealed something strange.

- There's a large stone with the word 'Max'

and the letter F chiselled into its surface,

as well as the name Meier. What is this thing?

- The Elbe is another one of Europe's major rivers.

It originates in the giant mountains of the Czech Republic

and traverses all of Germany before draining into the North Sea.

It's another vital river to Germany, the Czech Republic

and a few other countries.

But Meier is a traditional German name.

So why is that on a random stone in a river in the Czech Republic?

- Before the Second World War,

people that lived in this area were mostly ethnic Germans

who had started settling here hundreds of years previous.

In fact, Decín used to go by its German name, Tetschen.

But following the end of the war, Tetschen came to exist

within the borders of the relatively new state of Czechoslovakia.

- And it wasn't until after the Second World War,

when the government of Czechoslovakia

expelled these ethnic Germans, that this area

really became populated by Czechs.

So these inscriptions are definitely more than 80 years old.

But how much older? That's hard to say.

NARRATOR: Closer inspection of the stone

reveals inscriptions of several different years.

- This is really something: the earliest year

inscribed on the stone is 1417, but then there's 1616,

1707, and 1811.

Really, for hundreds of years, people have been carving

seemingly random numbers into this stone.

Something must have been happening at that time

for people to have bothered to do this. But what?

- This is obviously not some official engraving.

All the words and years are placed at random.

There seems to be no rhyme or reason,

nor are they trying to tell a story or provide a narrative

of a particular event. I mean, a lot can happen

within any given year.

- Take 1811, for example.

This was the period marked by the Napoleonic Wars.

At the time, Napoleon was at the height of his power,

poised to send his Grande Armee into Russia.

So why would a German-speaking person living in Decín

decide to commemorate that year here?

- At the time, Decín was under the control of the Austrian Empire.

They were about to side with Napoleon

in his disastrous invasion of Russia.

But the actual invasion didn't happen

until the summer of 1812. So whatever happened in 1811

must have been of a different nature than war.

NARRATOR: Less than 20 miles downriver from the Decín stone,

in Pirna, Germany, another large rock has emerged

from the river, owing to the low water levels.

- So here they have inscribed many different years.

Just like the Decín rock, they have a 1707 and an 1811.

So something must have been going on

that affected people at the same time

in different locations. - The thing is, though,

there are other dates inscribed here that aren't on the Decín rock,

for example, 1812 and 1835. What's so special about these years?

NARRATOR: Around 250 miles downriver from Decin,

close to where the Elbe opens up and runs into the North Sea,

the residents of the German town of Bleckede also find inscriptions

on a rock that emerged from the riverbank.

- This one is a little more informative.

It reads: "Geht dieser Stein unter, wird das Leben wieder bunter."

And that means, "When this stone goes under,

life will become colourful again."

- By this, the writer is referring to the stone itself,

meaning that when the stone is again submerged underwater,

life will be better. As we know, even today,

life gets hard when the river levels run low. Hundreds of years ago,

this would have made life really bad.

Could this have to do with drought?

- Back in the day, a drought could be disastrous

in ways that are hard for many of us to imagine today.

Crops would fail, food would become scarce.

Hunger would set in, and society would fracture.

- Having lived through it,

or marking such periods of difficulty

with the year it happened, as well as a hopeful message,

would make sense considering how difficult life was.

NARRATOR: An even closer inspection of the Decín stone

finally reveals a little more information:

apart from names and years, someone has written text in German.

- It says “Wenn du mich siehst, dann weine."

And that means,"When you see me, then weep."

This might seem somewhat cryptic,

but taken in the context of the inscription found at Bleckede,

It makes a lot more sense.

The writer refers to the river,

and all the years listed must have been years of extreme drought.

Basically, if you're able to see this stone, you're in trouble.

- Even though we're able to grow a lot more food

and feed enormous amounts of people,

it doesn't mean that technology will always save us

when the rivers run dry. The 2022 drought

was one of the worst in five centuries.

Chances are that we're going to get a few more like that

in the future. NARRATOR: The stones in the Elbe

commemorating years of drought are known as hunger stones.

Those who wrote the inscriptions

have provided future generations with warning calls.

Seeing the stones emerge from the river

should tell us that the environment isn't co-operating in a way

that we need it to, and that we should react accordingly.

Subitles by Sky Access Services