Unearthed (2016–…): Season 8, Episode 2 - Rome's Gate to Hell - full transcript
Experts investigate myths of a secret portal to hell in Hierapolis.
Hierapolis.
An extraordinary Roman city
built on top of mysterious,
dazzling white formations
of rock.
This city was a pearl among
the cities of the eastern
Roman empire.
This magnificent
place hides a dark secret.
Legend says that beneath these
streets lies the gate to hell.
Why do the ancients
believe this city
hides a portal to
the underworld?
What is the deadly truth
behind this terrifying tale?
Now, experts have rare access
to investigate this ancient
horror story
and use pioneering technology
to solve
a 2,000-year-old mystery.
In the hunt for answers,
we digitally reconstruct
this spectacular Roman city.
We track the footsteps of
priests and gods,
investigate strange skeletons,
and explore a lost
sacred space to unearth
the truth about the terrifying
Roman gate to hell.
This is the ancient city of
Hierapolis in western Turkey.
Perched on top of stunning
white cliffs
more than 500 feet high,
it's one of the most
picturesque cities
in the Roman world.
This street is
the main street of the city.
Visitors would come through
the north gate behind me,
pass through the city.
They would be very impressed
with all
the architecture of
the buildings that were here.
Mark Wilson has been
investigating the Romans
for 35 years.
He explores
this extraordinary city.
Hierapolis is founded by
Greek settlers before
the Romans take control
in 133 B.C.
After the Romans
take over the city,
they begin big infrastructure
projects, building institutions
like bath houses.
We have several theaters
that are built here,
so they transformed the urban
landscape of Hierapolis.
The Romans turn Hierapolis into
a splendid city
of 12,000 people.
They build gymnasia and temples,
a mile long, colonnaded street,
and one of the finest
amphitheaters
in the Roman world.
But behind the grandeur lies
a sinister presence,
a strange shrine to Pluto,
god of the underworld
and his hellhound, Cerberus.
Why are they here?
Do the Romans believe
this magnificent city
is home to the gate to hell?
Julian Bennett investigates
this 2,000-year-old mystery.
He searches for clues in
an account written by the Greek
geographer Strabo,
who visits Hierapolis
in the first century B.C.
Strabo describes a terrifying
place believed
to be the entrance to
the underworld.
According to Strabo,
this eerie place is home to
an invisible terror that
causes animals to drop dead.
Where is this fatal grotto?
And what causes
these creatures to drop dead
so dramatically?
Searching for answers,
Julian explores
the area around the main temple.
Next door to
the sanctuary of Apollo,
Julian finds a replica of
a magnificent statue of Pluto,
god of the underworld.
And beneath it,
an intriguing structure.
Julian believes this must be
the place Strabo describes.
It's called the Plutonium,
the place of Pluto.
When archaeologists
first unearth this site,
they find a carved
inscription that
dedicates it to Pluto
and his queen.
Beneath it is a gateway,
just like Strabo describes,
but it's blocked with stones.
Myth has it that these rocks
conceal an entrance
to the underworld,
a gateway filled with
the toxic breath of
the hellhound Cerberus,
sending anyone foolish enough
to enter to certain death.
Can there be any truth
to this tale?
When archaeologists remove
the stones that seal
the gateway, something
mysterious happens.
The strange deaths
explain why the ancients
think this is the gate to hell.
But how does it work?
What is causing
these sudden fatalities?
Mehmet Ekmekci
first began studying
Hierapolis in 1993.
He believes the bizarre
animal deaths
must be caused by some
natural phenomenon.
Mehmet investigates
the area around
the entrance to the Plutonium.
In Roman times, this was dry,
but now it's flooded.
Something in the water
catches his eye.
Carbon dioxide occurs
naturally in the air
and in water...
The air we breathe
only contains a tiny amount,
just 400 parts per million.
At higher levels, it's deadly.
How much carbon dioxide
is there here?
Just 50,000 parts per million of
carbon dioxide, or 5%,
causes respiratory problems.
10% carbon dioxide will cause
vomiting and loss
of consciousness.
20% can cause convulsions,
coma, and death in one minute.
After just a few seconds,
Mehmet is struggling to breathe.
The maximum
concentration of carbon dioxide
this machine can measure
is 100,000 parts
per million, or 10%.
In seconds,
the reading hits
the top of the scale.
When the air here is measured
with a higher
specification monitor,
it's revealed to be full of
the deadly gas.
Mehmet believes the
toxic levels of carbon dioxide
explain what kills the birds
and other animals.
But it's not
only unlucky passing animals
that are caught in this
deadly trap.
Ancient texts described this
site as a place of pilgrimage,
where worshippers come to
seek favor
from Pluto and witness
his power.
The priests exploit their faith.
They sell animals to
the pilgrims
and promise to sacrifice them
in their name.
They walk the animals
into the enclosure,
leading them up
to the gate to hell.
Here, as if damned by the gods,
the animals fall lifeless
to the ground
while the priests
magically survive.
The discovery of carbon dioxide
explains the bizarre
animal deaths
and the mystery
of the gate to hell.
But there's another mystery
to be solved.
If the carbon dioxide levels
are so lethal,
why don't the priests die, too?
Can further evidence here at
the Plutonium
reveal how they escape
its deadly effects?
The spectacular
Roman city of Hierapolis,
it's said to be home to
the gate to hell,
where toxic levels
of carbon dioxide
cause animals to drop dead.
But why don't people die, too?
A clue may lie in the design
of the Plutonium itself.
The Romans build a gate
around the deadly cave.
And an enclosed arena
in front of it.
At one end is a temple
believed to house Persephone,
queen of the underworld.
On the other side,
steps provide seating for
over 500 spectators.
The arena beneath them floods
with carbon dioxide
from the cave,
creating an invisible kill zone,
bringing hell to earth.
How can the audience
and the priests survive in
this theater of death?
To find out, Mehmet Ekmekci
investigates how
the deadly gases spread
through the arena.
He takes a closer look at
the seating area and measures
the carbon dioxide levels.
Here, the carbon
dioxide levels are less
than 10,000 parts per million,
or 1%.
Seated in the open air,
the spectators are well away
from the deadly gas.
But what about the priests?
How do they go right
into the cave
and survive when the animals
they are leading die?
Mehmet believes
the secret to the priests'
survival lies in the special
properties of carbon dioxide.
He uses a tower of burning
candles to test this theory.
Next, Mehmet fills the
jar with pure carbon dioxide.
The gas sinks to the bottom
and puts out the candles
one by one.
Carbon dioxide
is heavier than air.
Mehmet believes
this special property is what
allows the priests to survive
the deadly gas
when the animals die.
The characteristics
of carbon dioxide
mean the gas sits
close to the ground,
creating a toxic cloud
around the priests' feet.
It allows them to walk in
and out of the gateway
without dying.
Do the priests believe they are
really entering
the gate to hell?
Julian Bennett believes
they know the deadly gas
is dangerous.
The priests
likely believe the deadly
vapors rise straight from
the underworld.
But who are
these secretive holy men?
An intriguing Roman sculpture
could provide clues.
Attis is a tragic
figure whose story
inspires the Galli priests
and a bizarre ritual.
According to legend,
Attis betrays Cybele when
he falls in love with
another woman.
Enraged, the goddess
drives Attis mad,
and he castrates himself.
The Galli priests worship
Cybele by imitating Attis,
wearing long robes,
heavy makeup,
and bleaching their hair.
During a festival called
the day of blood,
they hold wild parties,
whip themselves,
and some even self-castrate.
The citizens of Hierapolis
are mesmerized by
the bizarre priests and their
miracles at the Plutonium.
The city attracts visitors
from far
and wide to witness
the spectacle.
But just at the entrance to
Hierapolis lie hundreds of
solemn monuments.
What are they, and what more
can they reveal about this
mysterious place?
The ancient city
of Hierapolis...
At its heart is a lethal gate
to hell,
where strange priests
perform deadly rituals.
Nearby, hundreds of
stone monuments line
the road that leads out of
the main gate.
What are they, and what can they
reveal about life
in this remarkable city?
Stretching for almost a mile,
it's a city of the dead,
with over 1,200 tombs...
Inside the chambers,
archaeologists find a mass of
human remains with
rich grave goods
like coins and jewelry.
Some tombs contain
up to 90 skeletons.
It's one of the largest
surviving cemeteries
in the Roman world,
the final resting place for
tens of thousands of people.
Who is buried here?
And why is this graveyard
so magnificent?
The state of preservation
and the number of tombs
here in the cemetery
is just spectacular
and totally unexpected.
Historian Mark Wilson
investigates why there
are so many lavish tombs here.
He first needs to find out
who they belong to.
A clue lies in an inscription
found on one of the tombs.
This tomb is erected by
a merchant by the name of
Flavius Zeuxis, and Zeuxis
is telling us, a bit boastfully,
that during his lifetime, he
made a passage around the tip
of Greece 72 times
on his way to Rome.
So this attests to the great
mobility of a person like
Zeuxis, who could make
so many trips like this
during his lifetime.
The inscription
suggests the tomb's owner
works in Hierapolis's
main industry.
Zeuxis is most probably
a textile merchant,
because the city was noted for
its textile production.
He's carrying his trade goods
between Hierapolis and Rome,
which is 1,100 miles away.
Many of the people
buried here are
made rich by the city's
lucrative textiles trade.
Mark believes this is
why so many
of the tombs still stand today.
These tombs would take
about 1 to
2 years' salary for the cost
of constructing them,
and so they invest
a lot of their resources
in building
these tombs that last
to this present day.
This cemetery is
so spectacular thanks to
the wealth of the city's
textile merchants.
They used the finest stone to
build magnificent tombs,
which helps the structures
survive for two millennia.
But why is this city such
a great place to make
and export cloth?
Mehmet Ekmekci investigates.
He believes the answer lies
in the stunning
white rock formations
on the edge of the city.
Travertine terraces
are naturally occurring
rock formations made from
calcium carbonate.
They form when natural
spring water
bubbles up out of the ground.
As it flows down the hillside,
it leaves behind
these white deposits.
Over 400,000 years,
the deposits build up
to create this spectacular cliff
1.5 miles long and more than
500 feet high.
Mehmet believes the natural
springs that form
the travertine are key to
Hierapolis's textile industry.
He investigates the water.
Fresh water
has a mineral content
of less than 200 milligrams
per liter.
Mehmet discovers some
water here has a mineral
content of more than 2,500
milligrams per liter.
It's rich in calcium carbonate,
the perfect ingredient for
fixing dye on fabric.
Thanks to this natural resource,
Hierapolis becomes famous
for its woolen fabrics,
dyed in vibrant shades
of red and purple.
But textiles alone don't explain
the wealth of Hierapolis.
A ruined bath house
in the city center
reveals another clue to
the city's success.
The mineral-rich waters are
channeled directly
into Hierapolis and create
a thriving trade.
Ancient Greeks
and Romans believe
the waters can cure diseases,
from asthma to eczema,
and flock here to be treated.
The spa industry
makes Hierapolis rich,
helping it grow into
a city of 12,000 people.
But not everyone who comes
here to be treated is cured.
Mehmet believes
some of them end up
in the magnificent tombs of
the cemetery.
Mineral-rich
hot springs for textiles
and bathhouses and a cave filled
with deadly gas make
Hierapolis rich and famous.
Can a strange geological
formation outside the city
reveal what causes
these bizarre natural wonders?
Ancient Hierapolis
is unlike any other Roman city.
It's home to bubbling
mineral springs,
dazzling white rock formations,
and a dark cave
that spews out lethal vapors.
This trio of geological wonders
is evidence of subterranean
forces at work.
Three miles deep
beneath the city
is a huge chamber brimming
with magma bubbling at almost
2,000 degrees Fahrenheit.
It heats the groundwater
above so
that it leaches minerals
from the rocks.
It becomes saturated with
carbon dioxide
and highly pressurized.
The immense heat
and pressure try to push
the water up,
but there's a thick layer
of rock separating it
from the surface.
How can it reach the cave in
the Plutonium and release
its deadly gas?
Erhan Altunel searches
Hierapolis for clues.
As Erhan investigates,
he discovers more
mysterious damage.
A water channel has been
torn in two.
For Erhan,
there's only one
possible explanation
for what causes
all this destruction.
Historical accounts
reveal that in 60 A.D.,
a huge earthquake hits
Hierapolis.
It completely destroys
the growing city
and two other nearby towns.
What causes all these
devastating earthquakes?
And can it explain the strange
gases that leak into the city?
A clue may lie in towering
40-foot-high cliffs
just outside the city walls.
A tectonic fault
is a fracture in the ground
that occurs when pressure
builds up in the earth's crust.
This one is called
the Pamukkale fault.
It's about 25 miles long.
When it moves,
it creates earthquakes.
It's this fault that
causes all the earthquakes
in Hierapolis.
The city sits on a ticking
time bomb.
Erhan believes this
mighty fault is also the secret
force that creates the mineral
springs and travertine terraces
and powers the deadly
spectacle at the Plutonium.
Smaller cracks in the city
center support this theory.
Hierapolis is built right on top
of a tectonic fault.
It runs for a mile through
the city center and directly
under the Plutonium.
The tectonic fault explains
the phenomena seen
at the Plutonium.
It causes cracks
that allow carbon dioxide
to escape directly
into the shrine.
It's also the force that powers
the mineral springs and creates
this breathtaking landscape.
The mystery of the gate to
hell has finally been solved.
But more mysteries remain.
After an earthquake
destroys Hierapolis,
in the first century A.D.,
what happens to the residents?
What can the famous oracle at
Delphi reveal about
this eerie city?
Hierapolis.
What happens to the city after
an earthquake destroys it
in 60 A.D.?
Julian Bennett investigates.
A first clue could lie
in the city's nymphaeum,
an ornamental fountain
near the temple of Apollo.
When archaeologists unearth
the fountain's foundations,
they make a surprise discovery.
Arches are a common
feature of Roman architecture.
They allow engineers to span
wide gaps and construct large,
complex structures.
But it's very unusual to find
an arch in the foundations of
a building.
Experts believe that,
like many of the buildings in
Hierapolis, this structure
is evidence that after
the earthquake wreaks its
destruction, the Romans
rebuild the city.
The ground beneath Hierapolis
is scarred by rips in the earth,
evidence of centuries
of earthquakes.
Undeterred, the Romans build
their city right on top of
these cracks, even some of
their finest buildings.
They bridge a crack
under the nymphaeum
with stone arches and build
its walls around them,
hoping this magnificent
fountain will stand
the test of time
and provide vital drinking
water for years to come.
Julian believes the
Romans know about earthquakes
and design their buildings
to withstand them.
But why are they
so determined to stay
in this dangerous place?
Mark Wilson returns to
the travertine terraces
to investigate.
The city of Hierapolis
is situated in a very
fragile but beautiful place.
And of course,
part of that fragility is
the fact that we're on
a very active seismic zone.
Mark believes
the travertines hold the key to
understanding why
the Romans go to
so much effort to stay
in a place like this.
Well, the location is
fantastic here,
because it's situated
on one of most beautiful
natural wonders in the world.
It's also on this natural
shelf looking
over a beautiful, rich,
fertile valley called
the Lycus river valley,
and even in antiquity,
it was a very fertile
farmland that
contributed to the richness of
this city.
The Romans'
decision to live here
isn't only a practical one.
There's also another
spiritual reason
linked to one of
the most important shrines
in the ancient world.
The legendary sacred site of
Delphi in Greece is
home to a grand temple
dedicated to the god, Apollo.
This is where the oracle
of Delphi makes
her famous predictions.
Deep inside the temple is
a chamber where
gas rises from a crack
in the ground,
just like in Hierapolis.
The oracle priestess inhales
this breath of the gods.
She enters a trance
and predicts the future.
The Greeks believe
the fault at Delphi
is a direct channel to the gods.
They believe the same
connection exists
at Hierapolis,
as the city's name makes clear.
The Greek word hieron means
holy, polis means city.
So Hierapolis means holy city,
and this is very much
connected to
these religious sanctuaries,
to Apollo, to Pluto.
Hierapolis has an
important spiritual connection.
Here and across the ancient
world, people seek out
fault lines and geologically
active areas
to be closer to
the divine powers.
The Plutonium provided direct
access to the underworld,
and so the residents here
truly believed that
they were in a place
related to the gods.
A fault crack
and poisonous gases
do not deter the later Romans.
In fact, they're two of
the area's main attractions.
But the power of the Plutonium
does not last forever.
What can an intriguing
structure high up on
a hillside reveal about what
happens to the gate to hell?
The Roman city of Hierapolis,
perched on top of stunning
white cliffs.
Do the forces of nature
that create
this incredible landscape also
cause the city's downfall?
Historian Mark Wilson
goes back to
the Plutonium to find out
how the story ends.
Today at the Plutonium, we see
the entrance to the underworld
totally blocked up.
But this is not from some
natural catastrophe,
but clearly due to
human intervention.
Mark investigates why the Romans
shut down this important
sacred site.
A clue to their dramatic
change of heart
could lie high up
on the hillside.
Here, he finds
a mysterious tomb.
Among the hundreds
of tombs in the cemeteries of
Hierapolis, the question is,
why is this one special?
Well, according to tradition,
on the hill behind us,
Philip the apostle
of Jesus Christ
was martyred around 80 A.D.,
and after his death,
his body was buried
in this tomb.
According to ancient
Christian texts,
Philip the Apostle arrives
in Hierapolis around 60 A.D.
With a disciple,
Bartholomew and his sister,
Mariamne.
Philip preaches
the teachings of Christ
and performs miracles
to cure the ill.
But the temple priests,
the Galli,
and officials see Philip
as a heretic.
They arrest him, whip him, and
drag him through the streets.
They nail Philip upside down
on a cross to die
and hang Bartholomew
by the hair.
In the first century
after Christ,
the old gods still rule
supreme in the Roman world.
In Hierapolis, the Galli,
with their deadly rituals,
preside over the Plutonium,
and Christians are persecuted
for their beliefs.
But over the next 300 years,
Christianity spreads across
Europe and the near east.
The emperor Constantine
legalizes Christianity,
and we see the beginning of
churches being constructed
throughout these cities by
the Christians who live in them.
So Christian religion
now becomes
the majority religion
in the Roman empire.
Gradually, the old gods die out.
And in the late fourth century,
pagan worship is
officially banned.
In the middle of 6th century,
we see the emperor Justinian
sending out a man by the name
of John of Ephesus,
and his mission is to destroy
any remaining pagan temples
and sanctuaries
in places like Hierapolis.
The temple of
Apollo is knocked down,
the Plutonium is blocked up,
and a huge church is built on
the site where Philip
the apostle is martyred.
Hierapolis becomes a center
of Christian pilgrimage.
Pilgrims who once came
to Hierapolis to offer
sacrifices to Pluto at
the Plutonium now come to
the tomb of Philip to venerate
this important apostle.
Hierapolis, once the city
of Apollo and Pluto,
is now the city of Philip
and Jesus Christ.
But the threat
that comes from the fault line
running through Hierapolis
is not over.
In the 7th and 14th
centuries, two more
huge earthquakes devastate
the city.
Eventually, it's abandoned.
The seismic fault line that
caused the Romans to build
the sanctuary to Pluto
and brought notoriety to
the city was the same seismic
fault line that eventually
caused the destruction of
the city and its abandonment.
In the end, the Roman
expertise in engineering
was no match for the forces
of nature.
Today, the ancient
gods may be cast aside,
the gate to hell closed,
but the powers that fuel it
still lie dormant
beneath the earth until
the day they may wake again.
The Roman city of Hierapolis,
home to a terrifying mystery,
a cave full of vapors
where animals drop dead.
But now the truth has
been unearthed.
Hierapolis sits on a crack
in the ground,
a natural wonder that is
the source of the city's power,
the agent of its destruction,
and the answer to the mystery
of the gate to hell.
An extraordinary Roman city
built on top of mysterious,
dazzling white formations
of rock.
This city was a pearl among
the cities of the eastern
Roman empire.
This magnificent
place hides a dark secret.
Legend says that beneath these
streets lies the gate to hell.
Why do the ancients
believe this city
hides a portal to
the underworld?
What is the deadly truth
behind this terrifying tale?
Now, experts have rare access
to investigate this ancient
horror story
and use pioneering technology
to solve
a 2,000-year-old mystery.
In the hunt for answers,
we digitally reconstruct
this spectacular Roman city.
We track the footsteps of
priests and gods,
investigate strange skeletons,
and explore a lost
sacred space to unearth
the truth about the terrifying
Roman gate to hell.
This is the ancient city of
Hierapolis in western Turkey.
Perched on top of stunning
white cliffs
more than 500 feet high,
it's one of the most
picturesque cities
in the Roman world.
This street is
the main street of the city.
Visitors would come through
the north gate behind me,
pass through the city.
They would be very impressed
with all
the architecture of
the buildings that were here.
Mark Wilson has been
investigating the Romans
for 35 years.
He explores
this extraordinary city.
Hierapolis is founded by
Greek settlers before
the Romans take control
in 133 B.C.
After the Romans
take over the city,
they begin big infrastructure
projects, building institutions
like bath houses.
We have several theaters
that are built here,
so they transformed the urban
landscape of Hierapolis.
The Romans turn Hierapolis into
a splendid city
of 12,000 people.
They build gymnasia and temples,
a mile long, colonnaded street,
and one of the finest
amphitheaters
in the Roman world.
But behind the grandeur lies
a sinister presence,
a strange shrine to Pluto,
god of the underworld
and his hellhound, Cerberus.
Why are they here?
Do the Romans believe
this magnificent city
is home to the gate to hell?
Julian Bennett investigates
this 2,000-year-old mystery.
He searches for clues in
an account written by the Greek
geographer Strabo,
who visits Hierapolis
in the first century B.C.
Strabo describes a terrifying
place believed
to be the entrance to
the underworld.
According to Strabo,
this eerie place is home to
an invisible terror that
causes animals to drop dead.
Where is this fatal grotto?
And what causes
these creatures to drop dead
so dramatically?
Searching for answers,
Julian explores
the area around the main temple.
Next door to
the sanctuary of Apollo,
Julian finds a replica of
a magnificent statue of Pluto,
god of the underworld.
And beneath it,
an intriguing structure.
Julian believes this must be
the place Strabo describes.
It's called the Plutonium,
the place of Pluto.
When archaeologists
first unearth this site,
they find a carved
inscription that
dedicates it to Pluto
and his queen.
Beneath it is a gateway,
just like Strabo describes,
but it's blocked with stones.
Myth has it that these rocks
conceal an entrance
to the underworld,
a gateway filled with
the toxic breath of
the hellhound Cerberus,
sending anyone foolish enough
to enter to certain death.
Can there be any truth
to this tale?
When archaeologists remove
the stones that seal
the gateway, something
mysterious happens.
The strange deaths
explain why the ancients
think this is the gate to hell.
But how does it work?
What is causing
these sudden fatalities?
Mehmet Ekmekci
first began studying
Hierapolis in 1993.
He believes the bizarre
animal deaths
must be caused by some
natural phenomenon.
Mehmet investigates
the area around
the entrance to the Plutonium.
In Roman times, this was dry,
but now it's flooded.
Something in the water
catches his eye.
Carbon dioxide occurs
naturally in the air
and in water...
The air we breathe
only contains a tiny amount,
just 400 parts per million.
At higher levels, it's deadly.
How much carbon dioxide
is there here?
Just 50,000 parts per million of
carbon dioxide, or 5%,
causes respiratory problems.
10% carbon dioxide will cause
vomiting and loss
of consciousness.
20% can cause convulsions,
coma, and death in one minute.
After just a few seconds,
Mehmet is struggling to breathe.
The maximum
concentration of carbon dioxide
this machine can measure
is 100,000 parts
per million, or 10%.
In seconds,
the reading hits
the top of the scale.
When the air here is measured
with a higher
specification monitor,
it's revealed to be full of
the deadly gas.
Mehmet believes the
toxic levels of carbon dioxide
explain what kills the birds
and other animals.
But it's not
only unlucky passing animals
that are caught in this
deadly trap.
Ancient texts described this
site as a place of pilgrimage,
where worshippers come to
seek favor
from Pluto and witness
his power.
The priests exploit their faith.
They sell animals to
the pilgrims
and promise to sacrifice them
in their name.
They walk the animals
into the enclosure,
leading them up
to the gate to hell.
Here, as if damned by the gods,
the animals fall lifeless
to the ground
while the priests
magically survive.
The discovery of carbon dioxide
explains the bizarre
animal deaths
and the mystery
of the gate to hell.
But there's another mystery
to be solved.
If the carbon dioxide levels
are so lethal,
why don't the priests die, too?
Can further evidence here at
the Plutonium
reveal how they escape
its deadly effects?
The spectacular
Roman city of Hierapolis,
it's said to be home to
the gate to hell,
where toxic levels
of carbon dioxide
cause animals to drop dead.
But why don't people die, too?
A clue may lie in the design
of the Plutonium itself.
The Romans build a gate
around the deadly cave.
And an enclosed arena
in front of it.
At one end is a temple
believed to house Persephone,
queen of the underworld.
On the other side,
steps provide seating for
over 500 spectators.
The arena beneath them floods
with carbon dioxide
from the cave,
creating an invisible kill zone,
bringing hell to earth.
How can the audience
and the priests survive in
this theater of death?
To find out, Mehmet Ekmekci
investigates how
the deadly gases spread
through the arena.
He takes a closer look at
the seating area and measures
the carbon dioxide levels.
Here, the carbon
dioxide levels are less
than 10,000 parts per million,
or 1%.
Seated in the open air,
the spectators are well away
from the deadly gas.
But what about the priests?
How do they go right
into the cave
and survive when the animals
they are leading die?
Mehmet believes
the secret to the priests'
survival lies in the special
properties of carbon dioxide.
He uses a tower of burning
candles to test this theory.
Next, Mehmet fills the
jar with pure carbon dioxide.
The gas sinks to the bottom
and puts out the candles
one by one.
Carbon dioxide
is heavier than air.
Mehmet believes
this special property is what
allows the priests to survive
the deadly gas
when the animals die.
The characteristics
of carbon dioxide
mean the gas sits
close to the ground,
creating a toxic cloud
around the priests' feet.
It allows them to walk in
and out of the gateway
without dying.
Do the priests believe they are
really entering
the gate to hell?
Julian Bennett believes
they know the deadly gas
is dangerous.
The priests
likely believe the deadly
vapors rise straight from
the underworld.
But who are
these secretive holy men?
An intriguing Roman sculpture
could provide clues.
Attis is a tragic
figure whose story
inspires the Galli priests
and a bizarre ritual.
According to legend,
Attis betrays Cybele when
he falls in love with
another woman.
Enraged, the goddess
drives Attis mad,
and he castrates himself.
The Galli priests worship
Cybele by imitating Attis,
wearing long robes,
heavy makeup,
and bleaching their hair.
During a festival called
the day of blood,
they hold wild parties,
whip themselves,
and some even self-castrate.
The citizens of Hierapolis
are mesmerized by
the bizarre priests and their
miracles at the Plutonium.
The city attracts visitors
from far
and wide to witness
the spectacle.
But just at the entrance to
Hierapolis lie hundreds of
solemn monuments.
What are they, and what more
can they reveal about this
mysterious place?
The ancient city
of Hierapolis...
At its heart is a lethal gate
to hell,
where strange priests
perform deadly rituals.
Nearby, hundreds of
stone monuments line
the road that leads out of
the main gate.
What are they, and what can they
reveal about life
in this remarkable city?
Stretching for almost a mile,
it's a city of the dead,
with over 1,200 tombs...
Inside the chambers,
archaeologists find a mass of
human remains with
rich grave goods
like coins and jewelry.
Some tombs contain
up to 90 skeletons.
It's one of the largest
surviving cemeteries
in the Roman world,
the final resting place for
tens of thousands of people.
Who is buried here?
And why is this graveyard
so magnificent?
The state of preservation
and the number of tombs
here in the cemetery
is just spectacular
and totally unexpected.
Historian Mark Wilson
investigates why there
are so many lavish tombs here.
He first needs to find out
who they belong to.
A clue lies in an inscription
found on one of the tombs.
This tomb is erected by
a merchant by the name of
Flavius Zeuxis, and Zeuxis
is telling us, a bit boastfully,
that during his lifetime, he
made a passage around the tip
of Greece 72 times
on his way to Rome.
So this attests to the great
mobility of a person like
Zeuxis, who could make
so many trips like this
during his lifetime.
The inscription
suggests the tomb's owner
works in Hierapolis's
main industry.
Zeuxis is most probably
a textile merchant,
because the city was noted for
its textile production.
He's carrying his trade goods
between Hierapolis and Rome,
which is 1,100 miles away.
Many of the people
buried here are
made rich by the city's
lucrative textiles trade.
Mark believes this is
why so many
of the tombs still stand today.
These tombs would take
about 1 to
2 years' salary for the cost
of constructing them,
and so they invest
a lot of their resources
in building
these tombs that last
to this present day.
This cemetery is
so spectacular thanks to
the wealth of the city's
textile merchants.
They used the finest stone to
build magnificent tombs,
which helps the structures
survive for two millennia.
But why is this city such
a great place to make
and export cloth?
Mehmet Ekmekci investigates.
He believes the answer lies
in the stunning
white rock formations
on the edge of the city.
Travertine terraces
are naturally occurring
rock formations made from
calcium carbonate.
They form when natural
spring water
bubbles up out of the ground.
As it flows down the hillside,
it leaves behind
these white deposits.
Over 400,000 years,
the deposits build up
to create this spectacular cliff
1.5 miles long and more than
500 feet high.
Mehmet believes the natural
springs that form
the travertine are key to
Hierapolis's textile industry.
He investigates the water.
Fresh water
has a mineral content
of less than 200 milligrams
per liter.
Mehmet discovers some
water here has a mineral
content of more than 2,500
milligrams per liter.
It's rich in calcium carbonate,
the perfect ingredient for
fixing dye on fabric.
Thanks to this natural resource,
Hierapolis becomes famous
for its woolen fabrics,
dyed in vibrant shades
of red and purple.
But textiles alone don't explain
the wealth of Hierapolis.
A ruined bath house
in the city center
reveals another clue to
the city's success.
The mineral-rich waters are
channeled directly
into Hierapolis and create
a thriving trade.
Ancient Greeks
and Romans believe
the waters can cure diseases,
from asthma to eczema,
and flock here to be treated.
The spa industry
makes Hierapolis rich,
helping it grow into
a city of 12,000 people.
But not everyone who comes
here to be treated is cured.
Mehmet believes
some of them end up
in the magnificent tombs of
the cemetery.
Mineral-rich
hot springs for textiles
and bathhouses and a cave filled
with deadly gas make
Hierapolis rich and famous.
Can a strange geological
formation outside the city
reveal what causes
these bizarre natural wonders?
Ancient Hierapolis
is unlike any other Roman city.
It's home to bubbling
mineral springs,
dazzling white rock formations,
and a dark cave
that spews out lethal vapors.
This trio of geological wonders
is evidence of subterranean
forces at work.
Three miles deep
beneath the city
is a huge chamber brimming
with magma bubbling at almost
2,000 degrees Fahrenheit.
It heats the groundwater
above so
that it leaches minerals
from the rocks.
It becomes saturated with
carbon dioxide
and highly pressurized.
The immense heat
and pressure try to push
the water up,
but there's a thick layer
of rock separating it
from the surface.
How can it reach the cave in
the Plutonium and release
its deadly gas?
Erhan Altunel searches
Hierapolis for clues.
As Erhan investigates,
he discovers more
mysterious damage.
A water channel has been
torn in two.
For Erhan,
there's only one
possible explanation
for what causes
all this destruction.
Historical accounts
reveal that in 60 A.D.,
a huge earthquake hits
Hierapolis.
It completely destroys
the growing city
and two other nearby towns.
What causes all these
devastating earthquakes?
And can it explain the strange
gases that leak into the city?
A clue may lie in towering
40-foot-high cliffs
just outside the city walls.
A tectonic fault
is a fracture in the ground
that occurs when pressure
builds up in the earth's crust.
This one is called
the Pamukkale fault.
It's about 25 miles long.
When it moves,
it creates earthquakes.
It's this fault that
causes all the earthquakes
in Hierapolis.
The city sits on a ticking
time bomb.
Erhan believes this
mighty fault is also the secret
force that creates the mineral
springs and travertine terraces
and powers the deadly
spectacle at the Plutonium.
Smaller cracks in the city
center support this theory.
Hierapolis is built right on top
of a tectonic fault.
It runs for a mile through
the city center and directly
under the Plutonium.
The tectonic fault explains
the phenomena seen
at the Plutonium.
It causes cracks
that allow carbon dioxide
to escape directly
into the shrine.
It's also the force that powers
the mineral springs and creates
this breathtaking landscape.
The mystery of the gate to
hell has finally been solved.
But more mysteries remain.
After an earthquake
destroys Hierapolis,
in the first century A.D.,
what happens to the residents?
What can the famous oracle at
Delphi reveal about
this eerie city?
Hierapolis.
What happens to the city after
an earthquake destroys it
in 60 A.D.?
Julian Bennett investigates.
A first clue could lie
in the city's nymphaeum,
an ornamental fountain
near the temple of Apollo.
When archaeologists unearth
the fountain's foundations,
they make a surprise discovery.
Arches are a common
feature of Roman architecture.
They allow engineers to span
wide gaps and construct large,
complex structures.
But it's very unusual to find
an arch in the foundations of
a building.
Experts believe that,
like many of the buildings in
Hierapolis, this structure
is evidence that after
the earthquake wreaks its
destruction, the Romans
rebuild the city.
The ground beneath Hierapolis
is scarred by rips in the earth,
evidence of centuries
of earthquakes.
Undeterred, the Romans build
their city right on top of
these cracks, even some of
their finest buildings.
They bridge a crack
under the nymphaeum
with stone arches and build
its walls around them,
hoping this magnificent
fountain will stand
the test of time
and provide vital drinking
water for years to come.
Julian believes the
Romans know about earthquakes
and design their buildings
to withstand them.
But why are they
so determined to stay
in this dangerous place?
Mark Wilson returns to
the travertine terraces
to investigate.
The city of Hierapolis
is situated in a very
fragile but beautiful place.
And of course,
part of that fragility is
the fact that we're on
a very active seismic zone.
Mark believes
the travertines hold the key to
understanding why
the Romans go to
so much effort to stay
in a place like this.
Well, the location is
fantastic here,
because it's situated
on one of most beautiful
natural wonders in the world.
It's also on this natural
shelf looking
over a beautiful, rich,
fertile valley called
the Lycus river valley,
and even in antiquity,
it was a very fertile
farmland that
contributed to the richness of
this city.
The Romans'
decision to live here
isn't only a practical one.
There's also another
spiritual reason
linked to one of
the most important shrines
in the ancient world.
The legendary sacred site of
Delphi in Greece is
home to a grand temple
dedicated to the god, Apollo.
This is where the oracle
of Delphi makes
her famous predictions.
Deep inside the temple is
a chamber where
gas rises from a crack
in the ground,
just like in Hierapolis.
The oracle priestess inhales
this breath of the gods.
She enters a trance
and predicts the future.
The Greeks believe
the fault at Delphi
is a direct channel to the gods.
They believe the same
connection exists
at Hierapolis,
as the city's name makes clear.
The Greek word hieron means
holy, polis means city.
So Hierapolis means holy city,
and this is very much
connected to
these religious sanctuaries,
to Apollo, to Pluto.
Hierapolis has an
important spiritual connection.
Here and across the ancient
world, people seek out
fault lines and geologically
active areas
to be closer to
the divine powers.
The Plutonium provided direct
access to the underworld,
and so the residents here
truly believed that
they were in a place
related to the gods.
A fault crack
and poisonous gases
do not deter the later Romans.
In fact, they're two of
the area's main attractions.
But the power of the Plutonium
does not last forever.
What can an intriguing
structure high up on
a hillside reveal about what
happens to the gate to hell?
The Roman city of Hierapolis,
perched on top of stunning
white cliffs.
Do the forces of nature
that create
this incredible landscape also
cause the city's downfall?
Historian Mark Wilson
goes back to
the Plutonium to find out
how the story ends.
Today at the Plutonium, we see
the entrance to the underworld
totally blocked up.
But this is not from some
natural catastrophe,
but clearly due to
human intervention.
Mark investigates why the Romans
shut down this important
sacred site.
A clue to their dramatic
change of heart
could lie high up
on the hillside.
Here, he finds
a mysterious tomb.
Among the hundreds
of tombs in the cemeteries of
Hierapolis, the question is,
why is this one special?
Well, according to tradition,
on the hill behind us,
Philip the apostle
of Jesus Christ
was martyred around 80 A.D.,
and after his death,
his body was buried
in this tomb.
According to ancient
Christian texts,
Philip the Apostle arrives
in Hierapolis around 60 A.D.
With a disciple,
Bartholomew and his sister,
Mariamne.
Philip preaches
the teachings of Christ
and performs miracles
to cure the ill.
But the temple priests,
the Galli,
and officials see Philip
as a heretic.
They arrest him, whip him, and
drag him through the streets.
They nail Philip upside down
on a cross to die
and hang Bartholomew
by the hair.
In the first century
after Christ,
the old gods still rule
supreme in the Roman world.
In Hierapolis, the Galli,
with their deadly rituals,
preside over the Plutonium,
and Christians are persecuted
for their beliefs.
But over the next 300 years,
Christianity spreads across
Europe and the near east.
The emperor Constantine
legalizes Christianity,
and we see the beginning of
churches being constructed
throughout these cities by
the Christians who live in them.
So Christian religion
now becomes
the majority religion
in the Roman empire.
Gradually, the old gods die out.
And in the late fourth century,
pagan worship is
officially banned.
In the middle of 6th century,
we see the emperor Justinian
sending out a man by the name
of John of Ephesus,
and his mission is to destroy
any remaining pagan temples
and sanctuaries
in places like Hierapolis.
The temple of
Apollo is knocked down,
the Plutonium is blocked up,
and a huge church is built on
the site where Philip
the apostle is martyred.
Hierapolis becomes a center
of Christian pilgrimage.
Pilgrims who once came
to Hierapolis to offer
sacrifices to Pluto at
the Plutonium now come to
the tomb of Philip to venerate
this important apostle.
Hierapolis, once the city
of Apollo and Pluto,
is now the city of Philip
and Jesus Christ.
But the threat
that comes from the fault line
running through Hierapolis
is not over.
In the 7th and 14th
centuries, two more
huge earthquakes devastate
the city.
Eventually, it's abandoned.
The seismic fault line that
caused the Romans to build
the sanctuary to Pluto
and brought notoriety to
the city was the same seismic
fault line that eventually
caused the destruction of
the city and its abandonment.
In the end, the Roman
expertise in engineering
was no match for the forces
of nature.
Today, the ancient
gods may be cast aside,
the gate to hell closed,
but the powers that fuel it
still lie dormant
beneath the earth until
the day they may wake again.
The Roman city of Hierapolis,
home to a terrifying mystery,
a cave full of vapors
where animals drop dead.
But now the truth has
been unearthed.
Hierapolis sits on a crack
in the ground,
a natural wonder that is
the source of the city's power,
the agent of its destruction,
and the answer to the mystery
of the gate to hell.