All language subtitles for Hidden.Beneath.the.Cities.S01E05.Labyrinths.and.Legends.1080p.DSNP.WEB-DL.DDP5.1.H.264-KHN_track3_[eng]

A mysterious tunnel
is revealed

below the streets of
Washington, D.C.

The corridor
ran about 60 feet

before ending
in a concrete wall.

Rusted hinges were the only
trace of a wooden door

that once led
to something beyond.

Someone had built
a multilevel labyrinth

beneath the ground.

The only question was why?

Archaeologists make
a startling discovery

beneath an Italian town.

An excavation
unearthed the facade

of a monumental chamber tomb.

It turned out to be
an ancient sarcophagus.

What they found was stunning.

Near a southwestern
Colombian town,

massive subterranean chambers
are uncovered.

The entire region
is heavily affected

by tectonic activity.

Earthquakes are
relatively common.

Could these chambers
have been built

as some form of protection
or even shelter

from some other threat?

Below the busy
streets of the world's cities

exists a hidden
realm of wonder.

Sprawling ancient complexes,

mysterious tombs,

top-secret military bases,

strange structures,

and lost artifacts

buried beneath our feet
and long forgotten

until now.

Underground marvels are
exposed to reveal what lies

Hidden Beneath the Cities.

Set between Maryland
and Virginia,

Washington, D.C. was defined
from the start

by a push and pull between
federal authority, local life,

and shifting visions of what
the capital should be.

In 1790,
George Washington chose the site

for a new federal district on
the Potomac and Anacostia Rivers

on land ceded by Maryland
and Virginia.

He appointed Pierre L'Enfant
to design a bold modern city

with grand boulevards,
ceremonial spaces,

and a central capitol.

It was all inspired by
L'Enfant's native city, Paris.

During the Civil War,

Washington's population swelled
from 75,000 to 200,000,

triggering sanitation crises

and a wave
of smallpox outbreaks.

In the decades that followed,

new streets, sewer lines,
and public parks

began to reshape the city.

Around the turn of the century

talk of a new Washington

reflected the city's
rapid transformation.

Gilded Age wealth
brought mansions

to the upland neighborhoods,

embassies and statues
lent a cosmopolitan air,

and in 1907 work began
on the National Cathedral.

Washington was becoming a place
everyone wanted to be,

from lobbyists and trade groups

to anyone hoping to shape
the nation's future.

In September of 1924,

a truck delivering
construction supplies

sinks into an alley behind
a house in the city.

When it's pulled free,

it reveals an opening
wide enough to climb inside.

This clearly
wasn't a sinkhole.

A nearby resident grabbed
a flashlight,

and along with a janitor,
went to take a look.

They climbed down into
the tunnel about four feet wide,

its walls lined with
white-enameled brick

with an arched
ornamental ceiling

rising nearly
eight feet overhead.

The corridor
ran about 60 feet

before ending
at a concrete wall.

Rusted hinges on the surface
of that wall were the only trace

of a wooden door that once
led to something beyond.

But it didn't end there.

A separate passage led down six
brick steps to a second tunnel,

which had a trapdoor
in the floor.

Beneath it, an iron ladder
vanished deeper underground.

Above ground,
onlookers gathered

as fresh cracks appeared,

exposing new entrances
to the hidden network.

No one could explain it,
and rumors spread fast.

Brick by brick,

someone had built a multilevel
labyrinth beneath the ground.

The only question was why?

As exploration
continues,

one detail stands out.

Inside the tunnel,

clues from a different era
begin to surface.

Pasted to the tunnel's
ceiling were German newspapers

from 1917 and 1918.

According to early
newspaper reports,

many referenced stories
about submarine activity

and had cryptic markings
that looked like ciphers.

Were these remnants of a covert
German intelligence network

operating beneath Washington?

It made sense
for people to be worried

about German espionage.

Back in World War I,
the Secret Service had seized

the briefcase
of Dr. Heinrich Albert.

He was Germany's chief financial
agent in America,

and he controlled
over $27 million for sabotage,

from strikes
and factory disruptions,

to poison gas, even plans for
a naval landing near New York.

Some neighbors
recalled a German chemist

who once lived nearby
and speculated the tunnel

had been used by spies to reach
his home during the war.

Neighborhood children said
the passengers ran to Rock Creek

and even dropped
into the sewers;

a possible escape route
for those who knew the way.

As investigators pushed deeper,

parts of the story
seem to line up.

One tunnel did track
toward Rock Creek.

Others branched off
in unexpected directions.

One skirted the home
of Washington Post owner

Edward B. McLean.

Another ended in
a walled garden,

and a third was blocked
with a cement door.

All of this was less than two
miles from the National Mall,

close enough to raise
genuine alarm

about spies operating
underneath Washington.

Over 4,000 miles
away in Berlin,

another tunnel reveals how
intelligence operations

can unfold entirely
out of public view.

Known as Operation Gold,

the Berlin Tunnel was built
between 1954 and 1955

by the CIA and Britain's MI6

to tap Soviet military
phone lines

carrying traffic between Moscow,
Warsaw and Bucharest.

Lined with 125 tons of steel,
it ran nearly 1,500 feet deep

across the border
into East Berlin.

The tunnel's entrance
was hidden

under a U.S. Air Force warehouse
in West Berlin.

When it was complete, British
technicians installed the taps,

and over the next 11 months,

intercepted hundreds
of thousands of calls

and millions of hours
of teletype traffic.

Much of it was
genuine intelligence,

despite the fact
that the Soviets knew

about the tunnel from the start.

In Washington,
early reports mentioned

electrical wiring
in the tunnel walls,

but its size and construction
were nothing like

the purpose-built
espionage tunnels in Berlin.

And unlike Operation Gold,
no records or credible accounts

ever linked it
to intelligence work,

meaning it might have
been concealed

for entirely different reasons.

As the discovery
dominates the headlines,

some wonder if the tunnels

serve a different kind
of clandestine network.

Early newspaper
reports claim that

an abundance of bottles
was found in the tunnel.

What you have to
understand about that

is that Washington enacted
Prohibition in 1917,

three years before Prohibition
at the national level.

So after that, the city's
267 licensed saloons

multiplied into nearly
3,000 speakeasies.

Hidden beneath candy shops and
tucked into drugstore basements,

they kept the capital
supplied with alcohol.

Could the tunnel have been part

of the city's illicit
trade in liquor?

Bootlegging in Washington

wasn't always discreet.

In one case, a Prohibition
Bureau agent found two men

unloading liquor
off Pennsylvania Avenue.

Shots were fired,
and a stray round

struck Senator Frank Greene
of Vermont,

an injury he never
recovered from.

In a city where the trade
was sometimes public,

a tunnel would have
offered bootleggers

the benefit of cover
and control.

From 1920 to 1930,
George Cassiday,

or "the man in the green hat"
as he was known,

was the primary bootlegger
for members of Congress.

He kept a basement office in the
Cannon House Office Building,

and later moved to the Senate

and made up to 25 deliveries
a day with near total freedom.

Despite arrests
in 1925 and 1930,

he never named his clients,

but claimed at least
80% of lawmakers

drank during Prohibition.

With demand that high
inside the Capitol,

a discrete route would
have obvious value.

Over 600 miles
northwest of Washington,

Milwaukee's residents
found similar methods

to bypass Prohibition
restrictions.

In 2021, renovations
at the historic Turner Hall

uncovered a cutout in the wall,
leading to a hidden room.

Many members of this athletic,
cultural, and political society

were part of Milwaukee's
German community,

which staunchly
opposed Prohibition.

Locals say that the space
was connected to a network

of tunnels linking
neighborhood bars,

some stretching all the way
to the Milwaukee River.

During Prohibition,
rumrunners from Canada

crossed Lake Michigan to bring
liquor into Wisconsin.

By 1928, the FBI had tallied
more than 1,100 speakeasies

operating in Milwaukee alone.

At Turner Hall,
traces of that era were found,

including handwritten notes,
recipes for hooch,

and personal effects
from drinking clubs.

Milwaukee's tunnels
show how hidden spaces

might have been used to fuel
a thriving underground economy.

But in Washington,

there's no sign
the Dupont tunnels

were built or used for profit.

And certain details there point
to a story that's way stranger

than anything behind
a speakeasy door.

Eventually,
the trail leads to one man

with a life as elaborate
as the tunnels themselves.

When the tunnels
were exposed in 1924,

some longtime neighbors
weren't surprised.

They'd seen them
seven years earlier

when a steam shovel broke
through the same property

which was once owned
by Harrison Gray Dyar, Jr.,

who was one of America's most
accomplished entomologists

and one of its strangest
scientific figures.

But why would a man devoted
to moths and mosquitoes

spend years meticulously digging
tunnels beneath his own home?

Born to a wealthy
New York family,

Dyar studied chemistry at MIT
and biology at Columbia.

In 1897, he moved
to Washington to oversee

the Smithsonian's butterfly
and moth collection

while living on his inheritance,

along with his wife Zella
and their children.

In 1900, their marriage
became strained.

Zella was struggling
with hearing loss,

and she didn't want to have any
more children, whereas Dyar did.

That same year,
Dyar began an affair

with a kindergarten teacher
named Wellesca Pollock.

A few years later,
Wellesca married another man.

And around that time,
Zella asked Dyar

for a hollyhock garden
at their home.

He began digging,

and didn't stop until he left
the property in 1914.

But it wouldn't be
his last time underground.

By 1915, the marriage
of the Dyars was collapsing.

He sued Zella for desertion.

She sued him for adultery.

Then, Wellesca tried to divorce
her long-absent husband.

This was a man
no one had ever seen

and whom many believed
was actually Dyar.

Rumors that he'd fathered
her three sons

turned out to be true.

And in 1917, that scandal
cost Dyar his job

at the Department
of Agriculture.

Four years later,
he married Wellesca,

and the digging began again.

Beneath the side yard
of their new home,

Dyar built an impressive bunker.

The tunnels and shafts
drop 24 feet,

with arched ceilings
and electric light

strung through the passageways.

Sculpted human and animal heads
stared from the walls,

and over one arch,
a Latin inscription read,

"The way down to Hell is easy."

Dyar's tunnels were
definitely strange undertakings,

but they weren't commercial
and they weren't criminal.

These were private environments
seemingly shaped for control,

comfort, and personal meaning;

though Dyar insisted
that his digging

was nothing more than exercise.

Dyar died of a stroke in 1929.

His tunnels were later used
for mushroom cultivation

and considered as World War II
air raid shelters,

before being demolished

for the Federal Aviation
Administration's headquarters.

The tunnels were partially
uncovered in 1958,

but then sealed.

In the science world,
Dyar is a bit of a big deal.

He named or co-named
almost 3,000 species

of moths and butterflies,

along with 600 different
kinds of mosquitoes.

And he's been honored
by having a whole bunch

of different insects named
after him, almost 70 of them.

But in Washington,
he's remembered differently.

He's the human mole, this
brilliant, defiant scientist

living a double life
above and below ground.

The bizarre tale of
Harrison Dyar and his tunnels

reminds us that in some
subterranean spaces,

the mystery runs deeper
than the complexes themselves.

And his story leaves
a broader question.

How many other hidden worlds
might still lie

beneath Washington
waiting to be uncovered?

Just over 100 miles from Rome,
in the northwestern part

of Italy's Campania region
is the city of Giugliano.

Giugliano is situated

on a fertile coastal plain

with a population
of over 120,000 people.

It's part of a string
of agricultural communities

in Campania that
have been active

for centuries in this area.

The city is also
part of a region

called the Campania
Volcanic Arc,

because there's a lot
of geological activity here.

Earthquakes regularly
rock the region,

and residents sometimes
experience daily tremors.

In 2025, Giugliano and its
surrounding area were hit

by their largest earthquake
in 40 years.

It's only a short
drive to Pompeii,

the town famous for being buried

by a devastating
volcanic eruption

from nearby Mount Vesuvius.

Giugliano is also
an area designated

for potential evacuation in case
of another devastating blast

from this dreaded volcano.

Just outside of town,

in a cluster
of volcanic craters

known as the Phlegraean Fields,

an archaeological survey
is being conducted

in advance of a planned update
to Giugliano's water system.

And the results are incredible.

An excavation
unearthed the facade

of a monumental chamber tomb

with a large piece of volcanic
rock covering its entrance.

Inside, the tomb
was a revelation.

The funerary chamber itself

was approximately
10 feet underground

and measured
around 10 by 13 feet.

The tightly sealed entryway had
helped keep the burial site

in a remarkable state
of preservation.

Two coffins were laid
on funeral beds,

and towering over them
were a number of frescoes,

including paintings
which depicted monsters

from classical mythology.

One fresco showed
the Greco-Roman god Hercules

and fellow deity, Mercury,

facing off against
the three-headed dog Cerberus,

considered to be the guardian
of the underworld.

The other featured two creatures
called ichthyocentaurs.

Half men, half horses
with green, coiled fish tails,

who were accompanied by two
winged, Cupid-like babies.

The colors of both paintings
remained incredibly vibrant.

And there were
other discoveries,

including three altars
called klinai

that held ceramic vessels

which would have been
used for libations.

There was also evidence
of cremated remains

beside the coffins.

To say this was an important
archaeological find

is an understatement.

The question is
who was buried here?

Archaeologists noticed

another mysterious object
in the tomb.

It appears to be
a table of some kind.

But they soon discover
it is much more than that.

It turned out to be
an ancient sarcophagus.

Before it was opened,

a miniature camera
was threaded inside

so that the contents could be
seen without being disturbed.

What they found was stunning:

an exceptionally well-preserved
human skeleton

laying on its back,
covered by a shroud.

Beside the remains
were grave goods,

like glass jars for
ointment and perfume,

as well as an instrument
called a strigil,

which ancient Greeks and Romans
used to scrape their skin clean.

The perfectly sealed
tomb created a micro-climate

that allowed for an incredible
level of preservation.

Interestingly, the artifacts
found inside the sarcophagus

were slightly older
than the artifacts found

throughout the rest of the tomb.

This suggests the individual
in the sarcophagus

was the first burial here and
likely the elder of the family.

The site is dubbed
the Tomb of Cerberus,

and an inscription marking
its final internment

to the year 27 CE places its
age at roughly 2,000 years old.

The tomb is not far from
the Roman colony of Liternum,

where over 300 veteran
soldiers retired

during the 2nd century BCE.

The Roman Empire was often
plagued by epidemics,

and traveling soldiers
in particular

could easily contract and spread
virulent diseases.

The infamous Antonine Plague
that exploded in 165 CE,

was reportedly killing 2,000
people a day at its height.

So maybe the body
in the sarcophagus

belongs to a high ranking
Roman soldier

who contracted some kind
of sickness while away fighting

and then was buried here.

The elder skeleton
was analyzed,

and herbs found on the body were
determined to be wormwood

and something called goosefoot,

both of which have purifying
and antiseptic qualities.

These ointments are believed
to have been used

to preserve the body.

But could they also have been
employed to treat disease?

And could the rock that sealed
the entrance to the tomb

had been put in place out of
fear that the contagions inside

might escape the burial site?

It's certainly
possible that the individual

in the sarcophagus was a soldier
who succumbed to an epidemic.

But the thing is, the Romans
would sometimes resort

to placing the dead from
a plague into mass graves

or hurried burials as the most
efficient form of internment,

and given the meticulous burial
in the Tomb of Cerberus,

this scenario seems improbable.

It's still a possibility

that they were
a high ranking soldier,

but maybe not one who died
from an epidemic.

The imagery found
within the tomb

and its location may point
to a belief in the occult.

The ancient Greeks
called this volcanic landscape

"the fiery fields," and within
Greco-Roman traditions,

it was considered to be
a physical gateway

to the afterlife.

The choice to place
the tomb here

suggests a deep understanding

of the spiritual importance
of this location.

The frescoes of Cerberus
and the ichthyocentaurs

are also potential signifiers

that the family who
controlled this tomb

knew the roles these
mythological creatures played

in the afterlife.

While Cerberus
was the guardian

of the underworld, Hades,

the ichthyocentaurs
had been interpreted to be

spiritual guides
who could escort the deceased

to the paradise of the so-called
Blessed Isles.

During this era,
the Roman Empire

certainly had its share
of mysterious cults

that possessed secret theories
about the afterlife.

So was the deceased
a high ranking member

of one of these groups?

It's highly plausible
that these cults,

known as "mysteries," had
a presence in this region.

Not far from the burial site

is the necropolis
of the town of Cumae.

Deep below the ground
is an ornate complex

where, according to legend,
an oracle would commune

with the Greco-Roman god Apollo.

Similarly, when the tomb
of Cerberus was built,

you can imagine that
the intention was to provide

the deceased with direct
communion with the gods.

Ultimately, though,
there's no evidence

that the individuals in the tomb
had any kind of membership

in one of the mystery cults
of the day.

Far from being representative
of a belief in magic

and the occult, the frescoes
in the Cerberus tomb

may simply be indicative of
an elite and educated family

that was well versed

in the fashionable cultural
signifiers of the day.

The status of
the family interred here

may ultimately be the key
to understanding the origins

of this enigmatic burial site.

This idea of a highly
honored senior member

of a wealthy clan is supported
by the incredible care

that was lavished on the body
found in the sarcophagus.

It's very possible that
they were a wealthy member

of the nearby
Liternum settlement.

The shroud,
the preservative ointments,

and instruments laid
around the remains

are all evidence of the respect
this person commanded

within their community.

Ultimately, much
about the Tomb of Cerberus

remains unclear.

A thorough scientific analysis
of the skeleton

may one day give us a better
idea of who this person was.

Until then, it seems
the three-headed monster

on the vibrant fresco
who stands guard

at the gates of the underworld,

is also protecting
the centuries-old secrets

locked inside
this mysterious tomb.

Tucked into
the remote reaches

of southwestern Colombia,

the Tierradentro National Park
spans several square kilometers

along the highest ridges
of the Colombian Andes.

The park is made up
of four distinct areas

that stretch along
the Andes Range.

The terrain is
incredibly variable,

ranging from 4,000 to more than
8,000 feet above sea level.

These steep elevation changes,

coupled with
the tropical climate,

create sudden and dramatic
shifts in weather

and temperature, often within
just a few kilometers.

The Andes are marked
by two principal rainy seasons:

one in the spring
and one in the fall.

Together, they bring nearly 60
inches of rainfall every year.

The rain helps sustain
the forests

that cover the mountains
themselves

and eventually drains
down to the valleys below,

enriching the soil
with sediment.

Tierradentro
also happens to be

one of the most important
archaeological sites

in Colombia;
but it's incredibly remote.

There are no flights
close to the area,

and the nearest city is about
a five-hour drive away.

The roads are rough,
cell phone service is patchy,

and the area is prone
to landslides,

which can make getting to
the site nearly impossible.

Nearly impossible,
but not totally impossible,

because the site has been the
subject of archaeological study.

When archaeologists began

to systematically investigate
the Tierradentro Park,

they uncover
a remarkable site

concealed beneath
the forest canopy.

Several meters
below the surface,

explorers uncovered
enormous chambers

carved right into the rock.

These ranged from
small structures

with a single small room

to massive 40-foot-wide chambers

with support columns.

These underground
chambers are a testament

to the engineering skill of
the people who built them,

especially given that
they were likely excavated

entirely by hand.

This was largely possible
because of the local geology.

The volcanic landscape
of the Andes

left behind thick layers
of hardened ash,

which formed a relatively
soft and workable stone.

Radiocarbon dating
tells us

that these underground chambers
were likely carved out

and used from
about 600 to 900 CE,

long before the Spanish
colonized Colombia.

But what exactly were
these structures for?

The underground
chambers' unique geography

and architecture point
to a possible explanation.

The name Tierradentro
was first used

by the Spanish conquistadors
back in the 1500s,

and it translates roughly to
"the interior land" or "inland,"

which fits because this region
is way off the beaten path.

It is tucked deep into
the mountains and forests,

far from the coast.

Now, why here?

Well, maybe the remoteness
was the whole point.

Maybe the ancient people built
these underground chambers

way out here and hid them
below ground for protection

or an edge against
potential invaders.

Looking back,
we can see several examples

of incredibly impressive
military fortifications

in the Andes Mountains.

One of the most famous examples
is Sacsayhuamán,

a massive Inca fortress

that sits above the city
of Cusco in Peru.

It was built during the 15th
century using huge stone blocks,

some of which reach
nearly 30 feet tall

and weigh several tons.

The fortress is so strong
that it survived earthquakes

that easily take down more
modern buildings in the area.

Because it was
so strategically important,

Sacsayhuamán played a huge role
in the Incas' last stand

against the Spanish
conquistadors.

Some of the most intense
and bloody battles

happened right here,

as the Incas tried
to hold on to their fortress.

In the end, the Spanish managed
to take control of Sacsayhuamán

after months of fierce fighting.

But there's another
legendary Andean site

that was so well hidden

the conquistadors
never even found it.

Machu Picchu stands
about 50 miles northwest

of Cusco, roughly 8,000 feet
above sea level.

It's a massive site
spread over 80,000 acres

of steep mountain
peaks and slopes.

Although it was probably
built in the 15th century,

Machu Picchu was essentially
unknown to the rest of the world

until a local took a professor
who was visiting

from Yale University to see it
in the early 1900s.

Machu Picchu is
actually made up

of hundreds of structures

including enormous fortifying
walls and terraces and ramps

that all blend
into the landscape.

It was most likely first built
as a royal residence

and a retreat
for the Inca elite,

but over the years,
it may also have served

a bunch of other religious
and spiritual functions.

Looking at
the Tierradentro chambers,

it becomes clear that they were
also intended for the elite.

Carving out these huge
underground spaces

required a significant amount
of organization and labor,

and wouldn't have been done
for just anyone.

But what was it for?

Was it like Machu Picchu,

a retreat for the ancient
upper class?

Or did it serve another,
more ritualistic function?

Nearly 1,000 miles away,

concealed deep
in the Peruvian highlands,

another set of extraordinary
underground chambers

raises intriguing
possibilities.

Chavín de Huántar is
the largest and most important

ruin left by the Chavín people:

an ancient culture
that predates the Inca

by more than 2,000 years.

The site stands more than
10,000 feet above sea level

and features a massive
stone temple complex

built out of huge
rectangular blocks.

The earliest part
of the complex

is known as the Old Temple,

and it was built in a distinct
U-shape around 900 BCE.

Several centuries later,
around 500 BCE,

the New Temple was added,
expanding the existing structure

and adding a massive
sunken plaza.

These plazas were central

to ancient Andean spiritual
and political power,

and would have been the site

of major religious
and ceremonial practices.

The site's
most unusual feature

sits beneath
the temples themselves,

where there's this
network of tunnels

and maze-like galleries
underground.

Some of them intersect,
some of them stand alone.

But these chambers are
in near total darkness,

with small tunnels,
maybe for ventilation,

but no windows to let
any daylight in.

Using computational
acoustics modeling

and careful reenactments,

a team of experts makes
an astonishing discovery.

These chambers
were likely built

with one thing in mind: sound.

Analyses have found that sound
waves travel extremely quickly

down the narrow passages,
bouncing off the walls

to fill the adjoining
alcoves and galleries.

The effect would have
been quite dramatic.

Music or human voices would
effortlessly fill the space

with little to no echo,

meaning that even if you were
standing far from the source,

you could hear
incredibly clearly.

The architecture of
the tunnels would have allowed

the Chavín to project this sound
out of the building itself

to pilgrims
in the plaza outside.

In effect, the entire building
would have seemed alive.

We can't be sure exactly
what these Chavín ceremonies

sounded like, but excavations
have uncovered

several ancient trumpets
made out of conch shells

that we've actually been able
to reproduce and record.

The intense soundscapes
from the galleries

weren't the only way

the Chavín enhanced
their ritual experiences.

Bone tubes that were once used
to inhale psychoactive plants

have also been found
in these galleries.

The combination of ritual drug
use and elaborate soundscapes

would have made for a truly
otherworldly experience.

So could the chambers
at Tierradentro

have served
a similar ritual purpose?

Based on
the existing evidence,

the chambers of Tierradentro
don't appear to have been carved

with acoustics in mind.

There are no plazas
to host crowds of pilgrims,

and to date, there's no evidence
of ritual drug use either.

But there are signs
that these were places

of profound
spiritual importance.

A closer look
at the architecture

of the Tierradentro chambers
reveals their true function.

Most of
the Tierradentro structures

have a central
staircase or shaft

that leads down
into a main chamber,

which is surrounded by a series
of side alcoves or niches.

These impressive
underground burial spaces

are known today as hypogea.

These were
grand collective tombs.

So instead of just one person,
entire elite families or clans

could be buried together
in the same space.

Grave offerings were left
with the bodies,

including gold ornaments,
ceramic pottery

and stone statues,

underscoring just how important
these people were.

Sadly, over the
centuries, many of these tombs

were looted and most of the
original objects are now gone.

But some artwork remains.

Bold black, red and white lines
zigzag and spiral their way

across the walls
in intricate geometric designs.

Some of the murals appear to
depict animal and human forms.

It's possible that
these represented gods

or guardians of some sort.

But their true symbolic meaning
remains a mystery.

Work is still
underway at Tierradentro,

where archaeologists continue
to piece together the story

of a civilization
that left behind

only its extraordinary,
ornate tombs.

180 miles northwest of London,

Liverpool stands
as one of Britain's

most historically
significant seaports.

Liverpool
was founded in 1207,

when King John granted a charter

for a new town
on the River Mersey.

Now, early trade with Ireland
helped it grow,

but by the 18th century

it had become a hub
of transatlantic commerce.

And there's a dark side to that.

There was this trade system
called the Liverpool Triangle,

in which manufactured goods
from Liverpool

were sent to West Africa to be
traded for enslaved people,

and those enslaved people
went across the Atlantic

to the West Indies,

where they were traded
for sugar and other crops.

The 19th century
brought explosive growth.

The Liverpool and Manchester
Railway opened in 1830,

the world's first
commercial passenger line.

The Albert Dock followed in 1846
with fireproof warehouses

and hydraulic cranes that cut
ship turnaround time in half.

During the Irish Famine,
thousands arrived by ship,

and by midcentury, Liverpool was
known as the New York of Europe.

In the 20th century,

Liverpool faced
disruption and decline.

Its port made it a target
during both World Wars,

and the city was hit hard
during the Blitz.

Post-war, the city faced
economic depression,

but Liverpool remained
culturally vital

from the Three Graces--

iconic buildings located
at the waterfront--

to the global explosion
of music and identity

that came with the Beatles.

In 2001, a small team
cuts through the roof

of a buried cellar

in the Paddington District
of Liverpool.

Lowered in by harness,
they find themselves

in a rubble-choked chamber,

an upper level of
a long lost passage.

Over the next two decades,

volunteers cleared tons
of soil, ash and debris,

revealing a hidden network

of at least 15 chambers
carved into sandstone.

Some are narrow crawlspaces,

just four feet wide
and six feet high.

Others are far more dramatic,

like the vaulted
banqueting hall,

and measuring
roughly 64 feet long,

14 feet wide and 27 feet high.

It reportedly connects to more
than two dozen other tunnels.

Paddington is one
of the deepest parts

of the network.

It's this stacked complex
of at least three levels,

dropping 56 feet below ground.

Brick pillars sit
on sandstone supports,

and according
to one old account,

the layout runs deeper than
the four-story building

that once stood above.

For decades,
the tunnels were mostly rumor,

until a rediscovered
1925 newspaper article

described a man
walking underground

for over a mile
beneath the streets,

reigniting public interest.

Earlier maps and surveys have
recorded parts of the system,

but later construction
buried much of it.

It wasn't until the mid '90s

that official archaeological
investigation began.

Computer scans now show
over 460,000 square feet

of map excavations,

spreading underground
in a spider-like pattern.

But the full extent of
the tunnels is still unknown.

So what kind of purpose
or obsession could justify

building a hidden world
beneath the city?

Inside the tunnels,
scattered artifacts

raise questions about
their possible use

and who was moving
through them.

These tunnels
don't look like spaces

that were simply quarried
and left behind.

Excavations have uncovered
hundreds of artifacts

like glass whiskey bottles
and stoneware jars.

Given the volume and variety,
is it possible these tunnels

supported contraband movement or
some form of underground trade?

In the late 1700s
and early 1800s,

smuggling was rampant
across Britain,

and it was fueled by high taxes

on things like tea,
tobacco and booze.

What began as
a small-scale evasion

grew into a full-blown
underground industry.

Smuggled spirits may have
at times outnumbered

the legal shipments coming
through London's docks.

Whole communities even
came up that rely entirely

on the economic benefits
of smuggling.

Beneath Liverpool,
some of the tunnels

are blocked or collapsed,

but they may have once
linked to larger features

like the Great Tunnel,

a vast chamber documented
in the 19th century.

In the 2000s, researchers
drilled into the site

in an attempt to relocate it,
but found nothing conclusive.

If the tunnel still exists,
it could suggest the network

was once organized
around a central hub,

built to move discreetly
between different areas.

Just northwest
of Liverpool in New Brighton,

a different underground network
reveals how tunnels

could support large scale,
secretive operations.

During World War II,
New Brighton's Seaside Arcade

concealed a full-scale
munitions factory below ground.

The tunnels, said to be around
100 years old at the time,

were cleared and converted
to house up to 200 women,

producing more than 250,000
bullets and shell casings

a week, all while the arcade
above kept up appearances.

The operation
was such a secret

that even Nazi bombing maps
failed to pick up the factory

beneath the arcade.

By 1943, the site also served
as a U.S. ordnance base,

assembling vehicles
and repairing equipment

from the Normandy front.

It was a vast covert network
right under the public's feet.

So the New Brighton
tunnels show that older spaces

could be adapted for covert use.

But there's no evidence
that the Liverpool tunnels

were built for this
or repurposed for this.

After 1815, the economics
of smuggling collapsed

as coastal blockades
strengthened,

and free trade policies
took hold,

it just didn't make
economic sense anymore.

And by the time the excavation
began in Liverpool,

smuggling was already
in decline.

So these tunnels were built
for a different purpose.

Other artifacts
suggest the tunnels

may have been designed
to sustain a long-term vision.

In ways,
these spaces seem designed

with daily life in mind.

Excavations have uncovered
bed warmers, chamber pots,

infant feeding bottles,
toothbrushes,

children's toys, and,
chillingly, bottles of poison.

More than 100 years of rubbish
was found in the tunnels,

some dating to a period shaped
by religious upheaval

and apocalyptic belief.

Is it possible these spaces
were meant for life to continue

underground after
everything above it ended?

The early 19th century

was steeped
in apocalyptic belief.

Movements like Millerism
took hold,

convincing tens of thousands
of followers

across the U.S.,
Canada and Britain

that Christ would return by 1844
to cleanse the world.

In that kind of climate,
digging a refuge underground

wouldn't have seemed
irrational at all;

it might have felt urgent.

Roughly 2,000 miles
from Liverpool,

in the village of Nikolskoe
in western Russia,

another underground structure
was built to outlast

what its creators believed
was coming above.

In 2007, a Russian
doomsday sect vanished,

only to be found
living in a bunker,

excavated more than 30 feet deep

into the snow-covered clay
and rock of Nikolskoe.

The group had
threatened to blow themselves up

with gas canisters
if forced above ground.

But when the roof
eventually gave way,

some took it as a sign from God
and climbed out.

The scene inside was haunting.

Sleeping spaces padded
with cardboard,

a kitchen carved into the rock,

and walls etched with drawings
of flowers and trees.

Even a chess set and children's
books were left behind.

While Liverpool's
tunnels and Nikolskoe

contain interesting artifacts,

and do share certain
architectural traits,

the underlying context
is entirely different.

Nikolskoe's underground network
was built

with a clear, apocalyptic
religious mindset,

but there's no evidence of that
kind of belief system

in Liverpool.

The motive here seems rooted

in a different kind
of long-term goal.

In the heart
of Liverpool's

19th century industrial boom,

a strange pattern
of construction

points back to a single figure.

In the early 1800s,
Joseph Williamson,

a wealthy, eccentric
tobacco merchant,

began developing land
in the area.

He modified houses
with bricked-up windows,

but the work didn't stop there.

His crews kept digging,
deeper and farther,

creating a vast tunnel network
with no clear purpose.

Williamson's name soon became
inseparable from the tunnels.

But what compelled him
to keep going?

By 1815,
the Napoleonic Wars had ended,

and Liverpool was flooded
with all these soldiers

coming back
with limited job options.

Now, by then, Williamson had
sold his tobacco business.

So he started hiring
all these soldiers to dig.

And for a lot of them,

that digging was the only
steady source of income

in a time when there
was just no other work.

As time went on,
the tunnels grew deeper,

more complex, and more aimless.

Some twist, stack,
or lead nowhere at all.

Men worked by candlelight with
picks, shovels, and barrows,

while carpenters
used axes and saws.

It's possible that the project

was less about utility
and architecture,

than it was hands-on training

in trades like masonry
and bricklaying.

If so, the tunnel's true value
wasn't in their purpose,

but in the livelihoods
they built.

There are all
kinds of theories

about Williamson's tunnels,

but he left no blueprints
or explanation.

After his wife died in 1822,

he added
domestic style chambers,

even a grand banquet hall.

For a man with no financial need
and no defined purpose,

the tunnels may have become both
his obsession and his escape.

Some argue
the so-called passages

likely began as open
sandstone quarries,

then covered and built over.

So in that view, Williamson
wasn't digging aimlessly.

He was reclaiming scarred land

and turning it
into something profitable.

But that still doesn't
explain the scale,

the chambers,
and the banquet hall.

If it started as
a quarry restoration,

it became something else and
something much harder to define.

Hidden beneath Liverpool,

Williamson's tunnels
remain a puzzle

of purpose and persistence,

a testament
to relentless effort

and to the blurred line

between visionary intent
and personal obsession.