Original subtitles

In Ybor City, Florida,

workers uncover hidden tunnels,

raising questions surrounding their purpose.

Who had the means,

who had the motive to build them?

And what might they suggest about the hidden activity

that once moved beneath Ybor City?

In Naples, Italy,

a hidden tomb is uncovered deep underground.

We believe the necropolis once held

dozens of tombs.

But key questions persist.

Who was buried here?

And what do these elaborate chambers tell us

about the Hellenistic Neapolis?

In Nushabad, Iran, a local digging a well

unearths a massive underground complex known today as Ouyi.

Ouyi had largely stayed hidden

from the modern world until its rediscovery in 2006.

And the question remains, why was it built in the first place?

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.

Three miles northeast of downtown Tampa, Florida,

lies Ybor City, a vibrant neighborhood born of industry

and shaped by immigrants.

But long ago, it was a haven for organized crime

where ambition and vice collided.

In 1885, Spanish-born magnate

Vicente Martínez Ybor moved his operations

from Key West to Tampa, pushed by labor unrest,

weak infrastructure, and political instability in Cuba.

Attracted by Tampa's rail lines and port,

he bought 40 acres northeast of downtown

and built a planned community of factories and worker housing,

laying the foundation for the city's rise

as an industrial powerhouse.

In 1896, cigar industrialists

expanded their reach by founding the Florida Brewing Company.

Set near key rail lines and Government Spring,

a crucial water source, the brewery thrived.

By 1900, it was reportedly exporting more beer to Cuba

than any other American brewery.

As Ybor City expanded,

so did Tampa's underworld.

From the late 1800s through the mid-20th century,

the city gained a reputation for organized crime

that was so entrenched that federal authorities ranked it

as one of America's most corrupt cities.

In November 2018, demolition crews

working at 12th Street and 6th Avenue in Ybor City

uncover a brick-lined tunnel, reigniting questions

about the neighborhood's rumored subterranean past.

The tunnel has rounded ceilings

and a flat, mostly dirt floor,

and modifications like intersecting pipes,

electrical wiring, and double locks.

Reinforced by three layers of brick,

the ceiling sits roughly one foot beneath street level.

While a small segment of the tunnel

was initially exposed during streetcar construction

in the early 2000s,

the 2018 excavation revealed additional details:

glass bottles, traces of a spring,

and a direct connection into the basement

of the Florida Brewing Company.

At least three tunnels

have been documented beneath Ybor.

At the former Blue Ribbon Store on 7th Avenue and 15th Street,

a local news report mentioned three separate passages

extending from the 26,000-square-foot building.

A fire in 2000 destroyed the building

and sealed any existing entrances,

leaving the extent of these tunnels unknown.

In a region where basements are uncommon,

these tunnels raise important questions.

Who had the means, who had the motive to build them?

And what might they suggest about the hidden activity

that once moved beneath Ybor City?

The straightforward design of the tunnels suggests

they might have initially served a practical purpose.

The tunnel discovered in 2018

appears to date to between 1885 and the late 1890s,

right in line with Ybor City's early expansion.

Structurally, it matches dual-use sewer systems

designed to manage both wastewater and stormwater

that were constructed in other US cities around that time.

Could the tunnels represent the city's first attempts

at sanitation and stormwater control?

In the 1700 and 1800s,

cities along the Eastern Seaboard

built brick storm drains that doubled as sewage channels.

Gravity would transport waste toward the bays or channels.

The tunnel discovered in 2018 likely once extended

directly to the Ybor Channel before being sealed off,

which supports the idea that it originally functioned

to carry wastewater toward the waterfront.

At the time, Tampa was experiencing explosive growth.

The arrival of the railroad in 1883,

the construction of the ultra-luxurious Tampa Bay Hotel

in 1891, and the rise of the cigar manufacturing

and brewing industries transformed the city.

By 1900, Tampa's population had tripled to 16,000.

Dealing with sewage and drainage

would have likely been a concern.

Roughly 1,000 miles north, in New York City,

similar challenges led to groundbreaking

infrastructure innovations.

By 1849, New York's population had surged

to nearly 500,000 people.

Sewage flowed into the rivers, and the city was struck

by one of its worst outbreaks of cholera.

In response, 70 miles of sewer pipe were laid

in just five years.

It's reasonable to think that other fast-growing cities

like Ybor may have looked to similar solutions.

In Ybor, a team laser-scanning the 2018 tunnel

found an artesian spring still flowing through the tunnel,

one that was documented nearly a century earlier.

While the spring alone doesn't confirm the tunnel's purpose,

its presence along with the drainage pipes

strongly suggests the structure was intended

for early water management or sewage.

Interestingly, some of the pipes

date to the 1970s or '80s,

indicating later reuse or modification.

While this particular tunnel was eventually identified

as a stormwater sewer on a 1927 city plan,

other tunnels don't appear in official records.

Some of the tunnels also have flat dirt floors,

which make them less effective for drainage.

While they may have started as part of Ybor's

early sanitation efforts,

more advanced systems were in place by 1905.

So it's possible their use evolved

beyond any original civic function.

Local lore, combined with the location

of the tunnels, has led some to question

whether they were built or later used for covert activity.

Even before national prohibition,

Florida had enacted its own ban on alcohol,

which meant that Tampa was dry.

But by the 1920s,

liquor arrived by boat from Cuba and the Caribbean,

and it also came in from local stills

across Hillsborough County.

Given the hundreds of bootlegging arrests on record,

could these tunnels have offered smugglers

a protected route underneath Ybor?

By 1930, Tampa had roughly

130 underground liquor retailers.

In Ybor, bootlegging became a thriving cottage industry.

Some estimates suggest half the neighborhood's families

were involved, as homemade stills supplied cafes,

restaurants, and speakeasies.

With that level of activity, the tunnels may have offered

a discreet way to move cash and contraband,

especially for Tampa's Italian community

who profited heavily from the trade.

That underworld economy overlapped

with the rise of mob figures like Charlie Wall

who built an empire on gambling,

and by the 1890s had taken over Tampa's Bolita Rackets,

an illegal numbers game with an 80-to-1 payoff,

reportedly with backing from local business leaders

eager to keep profits in the city.

By the 1930s, Italian bootlegging operations

were encroaching on Wall's territory.

A violent turf war broke out, and in the late '30s,

assassins tried to kill Charlie Wall in broad daylight,

blasting at his car with a sawed-off shotgun.

But Wall escaped into his home,

slipping through a tunnel-like passage

that linked his garage to the house.

In that climate, tunnels would have offered a secure way

to transport contraband

and an essential means of escape and protection.

Just 20 miles southwest in St. Petersburg,

another tunnel offers a possible glimpse

into how criminal networks in Florida

may have operated below ground.

Beneath the historic Snell Arcade,

a reinforced concrete tunnel

extends roughly 30 feet under the sidewalk.

It's only accessible through

a hidden four-square-foot hatch in the basement,

and Al Capone was rumored to have kept an office there.

During Prohibition, the Snell Arcade housed

a rooftop nightclub rumored to be a speakeasy,

and a taxi office linked to several moonshine arrests

in the 1930s.

Given that history, the tunnel may have offered

a way to move alcohol without drawing attention

from the police or the public.

While the Snell Arcade tunnel might have

initially served as utility access,

some suggest it continues beyond the basement wall,

possibly extending beneath the street toward a former bank.

This alignment has led some to believe that the tunnel

was later adapted for secretly transporting cash

or other contraband.

But here's the thing,

there's been no reported conclusive evidence

linking Ybor's tunnels to organized crime.

In the 1920s, public corruption and limited policing--

at times just nine officers for the entire city--

meant organized crime related to Bolita and Prohibition

could operate without relying on elaborate tunnel systems.

But that doesn't mean they didn't serve

another nefarious purpose.

Historians are now confident that Ybor's tunnels

originated as part of an early sewage system

abandoned by the city before the 1920s.

And while the passageways have never been definitively tied

to running contraband,

it's not a stretch to wonder if bootleggers and smugglers

used these secret corridors for their illicit purposes.

The tunnels beneath Ybor City offer traces

of a complex past and could illustrate a town

defined as much by what was hidden below ground

as by what built above it.

On the western coast of the Italian peninsula,

120 miles southeast of Rome,

Naples sits on the sweeping curve

of the bay that bears its name.

Naples sits within a natural arc of hills

that stretches from the promontory of Posillipo

to the Sorrentine peninsula.

This coastal setting helped define its long role

as a maritime hub, first in Greek antiquity,

and later as one of the Mediterranean's

most influential port cities.

Greek colonists arrived

between the 9th and 8th centuries BCE,

first on the island of Pithekoussai

and then later at Cumae on the mainland.

By around 600 BCE, they founded Neapolis, meaning "New City,"

a planned settlement with temples and a theater

and a major port, as well as a defined civic center.

Neapolis was absorbed into the Roman Republic

in 327 BCE, but retained autonomy for another 200 years,

allowing Greek customs to persist under Roman rule.

From the 6th century CE onwards, Naples transitioned

through Byzantine, Norman, and Swabian rule.

From 1265 on, under Angevin rule,

Naples flourished as a dynastic capital,

notable for its Gothic architecture

blending French, Greek, and Arab cultural elements.

In 1889, beneath the courtyard

of a 19th century palazzo in Naples' Sanità district,

a baron digging for water

pierces the ceiling of a long buried chamber,

uncovering one of the city's

most extraordinary archaeological sites.

40 feet below the palazzo, a steep staircase

leads to the Hypogeum of Cristallini Street--

four rock-cut tombs carved directly

into the volcanic rock hillside.

Each has its own monumental entrance.

One is even framed by ionic columns.

These entrances originally opened

onto the ancient necropolis pathway,

actively used between the 4th and 1st centuries BCE.

Each tomb follows a two-level plan.

The lower chambers built in the Hellenistic period

contain carved stone beds, statues, and symbolic offerings

consistent with traditional Greek burial customs.

Later Roman adaptations introduced niches for urns

and Latin inscriptions on the upper levels.

In all, 700 artifacts were discovered

reflecting the tomb's extensive and evolving use.

After centuries of activity,

flooding and mudslides buried the necropolis

beneath layers of sediment,

eventually concealing it entirely.

By the 1500s, the Sanità was built above it.

Now, workers may have encountered the site

in the 1700s, but even today, its full extent is unknown.

We believe the necropolis once held dozens of tombs.

The Hypogeum of Cristallini Street

opened to the public for the first time in 2022.

But key questions persist-- who was buried here?

And what do these elaborate chambers tell us

about the ancient beliefs, identity, and ramifications

of social status in Hellenistic Neapolis?

The vivid frescoes and symbolic motifs

inside the Hypogeum of Cristallini Street

raises questions about whether these tombs

were more than resting places.

The deepest and most intact chamber, Tomb C,

is framed by fluted columns, scarlet painted steps,

and elaborate frescoes.

The density of symbolic detail raises the question,

was this space designed for cultic ritual

or commemorative rites?

Dominating one wall is a 20-inch limestone Medusa head,

a common protective emblem in Hellenistic tombs

meant to ward off evil.

Nearby lies a silver wine jug

and meticulously carved offerings.

These features imply the chamber may have been

deliberately crafted to blend symbolic protection

with rituals of remembrance.

Near the tomb's entrance,

there's this painted golden dish that depicts two characters

who are believed to be Dionysus and Ariadne.

Those are characters associated with fertility, rebirth,

and divine ecstasy.

Now, there are also laurel and myrtle garlands.

Those are plants that are associated with Dionysus.

Unlike public ceremonies conducted at the civic level,

Dionysian mystery cults practiced private,

initiatory rituals for individuals or small groups

seeking favorable afterlives.

Cristallini's iconography may indicate

similar private rights were enacted here.

500 miles east at Amphipolis in northern Greece,

archaeological discoveries provide clear evidence

of ritual spaces dedicated to cult worship.

Excavations in 2024

beneath a later Byzantine basilica

revealed a dedicated cult building

reconstructed during the 4th century BCE.

Archaeologists found dense ritual deposits

including female figurines, womb effigies,

oyster shells, and animal bones,

indicating sustained cultic activities,

likely honoring a female deity, possibly Artemis.

Amphipolis provides definitive evidence

of cult activity-- votive offerings,

ritual objects, and a clear devotional setting.

While artifacts were found at Cristallini,

the most striking elements

are the carefully arranged architecture

and evocative imagery

raising an important archaeological distinction:

Is this a genuine cult space, or a commemorative tomb

that only mimics sacred ritual forms?

In 1968, about 50 miles southeast of Naples

at Paestum, the Tomb of the Diver was discovered.

The tomb is dated to around 480 to 470 BCE,

and it consists of five slabs of limestone

forming this small painted chamber.

The interior walls depict young men crowned with laurel

who are eating and making music.

But the most striking feature is the tomb's ceiling.

It shows this solitary figure diving headfirst

into shallow water framed by trees and by sky.

That image is unique.

It's unlike any other from that time in history.

The burial contents are unusually sparse,

with no human remains or inscriptions.

This absence of typical offering suggests that the tomb's meaning

may have relied heavily on its painted imagery,

with visual symbolism itself

serving as a key form of commemoration,

perhaps replacing material offerings.

Interpretations of the diver's imagery vary,

from metaphors on the soul's passage into the afterlife,

to depictions of suicide.

Some even argue these scenes were borrowed

from popular Attic face motifs,

and may not reflect a fully developed

or unified funerary belief system.

Cristallini, by contrast, represents

a more integrated ritual environment.

Its carved architecture and mythic iconography

points to deliberate planning

aimed at shaping commemorative practice.

But the limited evidence makes it difficult to determine

which rites or beliefs, if any, were actually tied to the space.

The architecture, materials,

and detailed iconography at Cristallini

hint at a particular social standing.

The tombs clearly reflect

high-status decorative traditions

observed in the 4th century BCE at Macedonian burials

and at Greek-speaking cities across southern Italy.

You've got monumental facades,

you've got richly painted interiors,

you've symbolic imagery--

all of that aligns with their customs and beliefs.

So, given these parallels, is it safe to assume

that these tombs were commissioned

by the prominent Greek families of Neapolis?

Hypogeum C exemplifies this substantial investment.

Carved directly into the rock,

its furnishings include stone beds

with intricate palmette and geometric patterns

resembling inlaid precious stones.

Painted pillows with carefully detailed red stitching,

along with expensive pigments,

like madder yellow and Egyptian blue,

reinforce the exceptional resources of the tomb's patrons.

Perhaps the strongest evidence of Greek patronage

lies in the Greek inscriptions of personal names

and six headstones bearing the word khaire, meaning farewell.

These inscriptions, coupled with sophisticated design elements,

indicate a deliberate expression

of cultural identity and elite status.

Over 450 miles south, the tholos tombs at Pylos

highlight a different approach to elite burial practices.

Excavations at Pylos uncovered

two beehive-shaped tombs 15 feet underground

and dating back 3,500 years.

Although looted in antiquity,

the chamber floors were once lined entirely in gold foil.

It was clearly intended as a powerful visual statement

of wealth and prestige.

Look at these artifacts.

You've got Baltic amber, you've got Egyptian amulets,

you've got a gold pendant

depicting the Egyptian goddess Hathor, protector of the dead.

There's a pattern to these.

They are rare, and they're imports.

Those two things suggest that early rulers

deliberately displayed objects like this

to broadcast their trade connections

and their cosmopolitan tastes.

This outward-facing strategy

contrasts with Cristallini's more narrow focus

that linked them back to their Hellenistic roots.

At Cristallini, elite status was asserted

not through lavish foreign goods,

but through culturally specific visual narratives, inscriptions,

and localized symbolic motifs,

indicating a tightly defined community identity

rather than a broader Mediterranean cosmopolitanism.

In 2023, archaeologists uncovered

the remarkably intact tomb of Cerberus,

dating to around 2,200 years ago,

just over 10 miles west of Naples.

The tomb's painted garlands

and vivid mythological scenes

include a rare depiction of Hercules capturing Cerberus,

the three-headed hound of the Roman underworld.

The tomb's impressive scale and intricate imagery

suggest it was commissioned by an elite family

for a prominent Roman patriarch in ancient Liternum.

Inside, archaeologists found libation vessels,

glass ointment jars, and a strigil,

which is a grooming tool used by ancient Greeks and Romans

in bath rituals.

Based on these findings,

it seems that the tomb's "lavish" elements

were strategically chosen to assert the social standing

and enduring legacy of its occupant.

At Cristallini, imagery of Dionysus

could also reflect elite status,

particularly for families involved in the wine trade.

Because in Hellenistic southern Italy,

Dionysus embodies big-picture themes

like transformation and immortality,

but he's also explicitly linked to wine and rituals around wine.

So this imagery could be doing two things at once here.

It could be signifying spiritual aspirations,

but also professional and economic identity.

The visual language at Cristallini

corresponds with philosophical ideas

circulating in southern Italy at the time.

From 530 BCE onwards, Pythagorean philosophy

was centered in southern Italian cities like Kroton,

and likely influenced local views of immortality,

cosmic order, and the afterlife.

Although a direct link can't be established,

these ideas may have informed how some elite community

used tombs to express beliefs in harmony, identity,

and continuity beyond death.

Around 20 Hellenistic tombs have been documented

beneath Naples' Sanità district,

but the Hypogeum of Cristallini is by far the most intact.

Still, questions remain about the individuals

behind its construction, their motivations,

and the precise beliefs embedded in its design.

Deep inside central Iran's Isfahan Province,

about six miles north of the historic city of Kashan,

is the desert town of Nushabad.

Now, as I understand it, the Persian name Nushabad

is traditionally translated as something like

"city of cold, tasty water."

And listen, in this part of the world,

cold water is gonna taste really good.

The climate is very hot.

But Nushabad's 12,000 or so inhabitants have been using

a freshwater spring at the foot of the nearby mountains.

And for more than 1,500 years, that underground water system

has supported not only drinking water,

but also agriculture and even public baths.

But the design of the city itself is also ingenious.

Towering over the streets are vertical towers

called wind catchers, which are designed to harness

the slightest breeze and funnel it indoors.

These impressive structures have towered above

Nushabad's desert skyline for centuries,

but in 2006, an accidental discovery shines a light

on what lies beneath this ancient city.

A local resident in a nearby village

was digging a well on his property

when he unearthed what appeared to be an underground tunnel.

Upon closer inspection,

it was clear that this was a man-made corridor

that had been cut into the earth and rock.

By 2007, formal excavations had begun,

and what they found at the end of this tunnel

would blow your mind.

It's this Byzantine complex of interconnected rooms

with three stories of narrow hallways and stairwells

that led to this dense concentration of hidden chambers

and canals going all the way down between 13 and 60 feet.

Each room had a height of approximately six feet,

which strongly suggested they'd been designed

for human occupation.

But there didn't appear to be a main entryway

into this underground city.

As the site was more thoroughly investigated,

a number of secret entrances were discovered.

These doorways were cleverly concealed

within some of the town's older residences.

The scale of this thing is enormous.

It's estimated to be over three and a half acres,

and it seems to have been dug out continuously over years.

But who built it, and why?

Researchers date the structure

by examining its architectural details,

along with stone tools and pottery

that were excavated from the site.

Their analysis places the construction

of this underground edifice to about 1,500 years ago.

This was the era of the Sasanian Dynasty in Iran.

The Sasanians were one of the most influential empires

in that country's entire history.

Under their regime, academia flourished

and an artistic renaissance began to bloom.

Archaeologists have found evidence of expert metalwork

and gem engraving

from this period.

Nushabad itself was situated

along a valuable trade route

between Tehran

and the Persian Gulf,

which was part of the Silk Road.

This made the city a valuable stop

for travelers and merchants alike.

To this day, there are ruins of centuries-old inns

buried in the surrounding desert.

But Nushabad's geographical location

also made it vulnerable to attack.

During the 7th century's Muslim conquests,

the Sasanians were crushed by the Arabs.

But evidence suggests the underground city of Nushabad,

which had been built during their reign,

continued to be extensively used for hundreds of years.

The subterranean underground world was locally known as Ouyi.

But despite its incredible size

and 1,500-year history, Ouyi had largely stayed hidden

from the modern world until its rediscovery in 2006.

And the question remains, why was it built in the first place?

A subterranean complex hints at subterfuge,

and there may have been a good cause for secrecy

in Sasanian Iran.

The kingdom adopted Zoroastrianism

as its state religion,

and while there was tolerance for other beliefs,

some did face religious persecution.

One such religion might have been Mithraism,

which was gaining popularity in Rome

at the same time Christianity was exploding across the empire.

Mithraism was inspired by the Iranian deity Mithra,

and worshipers would congregate

at these underground temples called Mithraea.

There's almost no literary evidence of Mithraic practices,

but hundreds of these temples have been discovered

in underground chambers

throughout the former Roman Empire.

In the northwestern part of the country,

the Mithra Temple of Maragheh features multiple rooms,

domed ceilings, and a grand entrance corridor.

It's possible Nushabad's Ouyi also could have served

as a secret place of worship.

But there's been no reported discovery

of any Mithraic artifacts or iconography

at Nushabad's underground city.

And a dedicated Mithraeum was usually only about 75 feet long

and 30 feet wide.

It would have held no more than 20 or 30 people,

far fewer than the sprawling complex buried under Nushabad.

The harsh living conditions in the desert

may have been motivation enough

for the construction of an underground city.

One obvious reason to build a complex of this size

below ground is to shield the people

from the punishingly hot weather you get in that region.

The structure's cooler temperature was achieved

by this brilliant series of air ducts throughout the complex

that could circulate the cooler air.

The complex appears to have been built

around the freshwater spring that was the town's namesake,

and it used water pipes and canals

to move the water from one place to another.

This was part of an ancient Iranian water system

called a qanat, which delivered groundwater to the surface

through a series of gently sloping underground tunnels.

It's highly plausible that the need to get cool air

and fresh water to its residents

in the most efficient way possible

is what drove the design of this structure.

And while the structure itself may appear

too grandiose for such a utilitarian purpose,

architecture during the time of the Sasanians

could be over the top.

But the sheer scale of this underground complex

betrays a larger, more important purpose.

The secret entrances into the underground suggest

that residents could quickly and easily go into hiding.

But why?

The town of Nushabad may have created

this mysterious habitat

as a means of escaping an imminent threat.

Around 1220, Genghis Khan,

the leader of the Mongolian Empire,

marched his armies into the Khwarezmian Empire

which included much of present-day Iran.

Now because of Nushabad's proximity

to a valuable trade route, it was a likely target.

The city's giant underground shelter could easily have served

as a wartime refuge for its residents.

By entering through secret entrances above ground,

the population could effectively disappear from view.

And because of the access to the spring water,

people could have sustained themselves there

for weeks at a time.

There are also many architectural details

throughout the halls that were clearly built

for defensive purposes.

One of the more ingenious features is the corridors

between the interconnected rooms, which are often angled

to eliminate direct sight lines between spaces.

This would make it much easier to hide from your enemy,

or conversely, it's the ideal space

to mount a surprise defensive maneuver.

In certain corridors,

there's also evidence of booby traps and disguised pits,

which could ensnare unsuspecting intruders.

Whether it was built in the time

of the Sasanians' conflicts with the Romans

or during their later battles with the Mongols,

the fact that this shelter and water system

were hidden underground strongly suggests

that safeguarding Nushabad from invaders

was the main reason it was built this way.

Today, researchers believe that this

enormous structure may be even larger than previously thought.

Currently, locals and tourists can enter

the underground city through an adjacent cistern,

but this isn't thought to be the original entrance.

So there's a very real possibility

that this underground network of tunnels

may extend far beyond the walls of Nushabad.

Many of the rooms were amalgamated

in the centuries following the Sasanian Dynasty,

and modern infrastructure, such as water pipes, storage spaces,

and even toilets, were eventually incorporated.

This complex is a wonder of engineering

that was continually updated

right until the beginning of the 20th century,

until it was reportedly abandoned in the 1920s.

It took the accidental discovery in 2006

for current generations to bring their own ingenuity

and adaptations to this incredible underground city.

Today, the site is recognized as one of the oldest

underground structures in the world.

And as researchers continue their exploration,

new mysteries are likely waiting to be uncovered

within Nushabad's secret subterranean city.

Situated near the center of Italy

and within 200 miles of iconic cities like Naples and Florence

is the nation's capital, Rome.

Rome is one of the most prominent centers of culture

and power in the history of the world.

And there's a reason that it's known as the Eternal City.

It's existed for almost 28 centuries,

making it one of oldest cities in Europe.

And within Rome, there's the sovereign country

of Vatican City, which is the administrative center

of the Catholic Church.

For centuries, the Roman Empire was a colossus

of cultural and economic power.

At its height, it spanned about 2 million square miles,

with its highly professionalized military controlling territory

in Western Europe, the Middle East, and Northern Africa.

At one point, Rome ruled over 60 million people,

which at the time was more than 20% of the world's population.

Today, 1,500 years after the fall

of the Roman Empire, the city is an archaeological gold mine.

Priceless artifacts are pulled out of there every year.

In 2016, the city is in the middle of undertaking

an excavation of a different kind.

The Metro C project is a years-long expansion

of public transportation from Rome's eastern suburbs,

but the construction of one of its underground tunnels

leads to an unexpected discovery.

Near the Aurelian Walls on Rome's Caelian Hill,

workers came into contact with a large structure

buried 30 feet below ground.

Archaeologists were brought in to conduct their own analysis

and excavation and soon realized that what they were looking at

was the remains of a large military complex

spanning over 9,000 square feet

and containing 39 dormitory-style rooms.

Two years later, they announce the discovery

of another mysterious building,

buried below the barracks at a depth of about 40 feet.

It appears to be the remains

of a luxurious Roman house, or domus.

Like the barracks, these remains are remarkably intact,

but their lavish decor stands in stark contrast

to the military building.

There's evidence that suggests the home

was deliberately dismantled and covered up.

The walls were raised and the room seemed to have been

carefully and purposefully filled with earth.

This is not your typical Roman ruin.

This house appears to have been intentionally buried.

So who lived in this place and why was it buried?

As the excavation continues, it becomes evident

that the domus was designed for comfort.

The house covers an area of about 3,000 square feet

with 14 rooms.

It also looks like the property had a large courtyard

with a fountain and a bath house.

Even by today's standards, this was a pretty sweet pad.

The interiors of the home are no less decadent.

Many of the rooms have floors

covered in black and white mosaics

made from marble and gray slate.

And there are two rare figurative mosaics as well.

One panel depicts a solitary bird perched on a branch.

Another depicts two figures, possibly deities,

who appear to be locked in combat.

Further excavation places the construction

of the house and the barracks in the 2nd century BCE

during the reign of Emperor Hadrian.

In this century, Caelian Hill,

where the barracks and domus were discovered,

was an area with a conspicuous display of wealth and power.

The Roman emperor's secret police,

known as the frumentarii, were stationed here,

as were the emperor's horse brigades.

The city's firefighters and police forces

were also located on Caelian Hill.

The hill was also a fashionable neighborhood

for the city's aristocracy.

And given the amenities in the courtyard of the buried house,

the mosaics and the private bath house,

it's clear that they likely belonged

to one of Rome's elites.

The fact that the home was situated

within the barracks grounds on Caelian Hill suggests

that the resident could have been a Roman senator

with connections to the military.

A politician living in this domus

would have effectively had their own private security force

living on the property with them.

Is it possible that this individual was caught

in some kind of intrigue or political upheaval

and needed protection?

In 271 BCE, Caelian Hill was home

to a violent uprising when workers at the mint revolted.

The emperor implicated several senators in the plot,

and they were eventually put to death.

Could one of those senators have been the owner

of the domus behind the barracks?

If so, the burial of his opulent home

may have followed soon after his execution.

If this senator had loyalists inside the barracks,

it's conceivable he could have taken up residence there.

But maintaining a private army

in the middle of one of the most powerful and influential regions

in Rome would hardly have gone unnoticed,

nor would it have been acceptable

to the neighboring power brokers,

much less the leaders of the military.

The burial of the barracks and the domus

may have been a public erasure.

Edicts like this were well within the powers of the state.

There was this formal punishment in the Roman world

called damnatio memoriae,

which means "condemnation of memory."

And this was a death penalty, but it was more than just that.

It also removed a person from the public record.

A perceived traitor within the ruling class would be executed,

and then their name would be removed from any inscriptions

and public monuments.

Their statues and their property would also be demolished.

Is it possible that this is what happened

to the owner of the mystery house?

The buried villa certainly suggests some kind

of deliberate erasure has taken place.

Whoever lived in the domus prior to its burial may have been

under house arrest and watched over by military guard

until his scheduled execution.

However, there is no physical evidence

to corroborate the theory.

Ultimately, the best explanation

for why this luxury home was nestled on military grounds

may be the simplest one.

The proximity of the luxury home

to the military barracks seems like it should tell us a lot

about who lived here.

In this context, it seems highly likely

that this was the private residence

of the commanding officer of the adjacent barracks.

It wouldn't have been unusual for a Roman general

to have lived in luxury.

A commander's residence was known as a praetorium,

and it was essentially the nucleus

of any military facility.

A praetorium that was unearthed at Castor in Cambridgeshire

was truly palatial and one of the largest structures

from the Roman Empire ever discovered in England,

far exceeding the size of the mysterious villa

on Caelian Hill.

If the buried domus in Caelian Hill really was

the home of a high-level military officer,

that would make it the first time within the city of Rome

that a military barracks has been found

with the private residence of its commander.

But the mystery of why

it was deliberately buried remains.

It would have taken a lot of effort

to cover up the domus, so what was the motivation to do so?

Both structures have now been painstakingly taken apart

and removed piece by piece; but the plan is to rebuild them

when the transit stop is completed.

Romans of today will be able to puzzle over the remains

when the domus and the barracks are reinstalled

near the metro station.

The questions surrounding the barracks

and its neighboring villa may never be fully answered.

For now, it seems the people who buried

these mysterious structures have successfully erased

their true origins from Roman history.