Original subtitles

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.