Original subtitles

Narrator: A massive storm

Reveals a lost underwater metropolis.

Arya: How about rediscovering the city?

That's unbelievable.

Narrator: The sunken city of neapolis,

Once a vital port for the sprawling roman empire.

Arya: With supply and demand,

Neapolis is just going to grow and expand.

Narrator: And the key to its success:

A must-have ingredient

That came to symbolize roman identity.

Lowe: This is the ketchup of the roman world.

Narrator: Experts are piecing together

The untold story of neapolis

And how it became essential to the roman war machine.

Arya: It's about location, location, location.

Narrator: Before a mysterious disaster

Wiped it from history.

Jackson: The ground turns to fluids and the city disappears.

Lowe: It's devastating.

Narrator: Hidden by the waves for over 1,500 years,

The ruins of neapolis are revealing secrets

Of the rise and fall of the world's greatest empire.

Lowe: Once the roman empire breaks down, the world shrinks.

(dramatic orchestral music)

Narrator: The relics of the past hold secrets.

(stones rumbling)

Written in gold, (hammer clinks)

Stone, (instrument clinks)

And blood.

We can unlock them.

These are the secrets of history's greatest treasures.

(dramatic orchestral music)

(tense orchestral music)

Tunisia, north africa.

Today, a popular tourist destination

By the mediterranean sea.

But 2,000 years ago,

This african country was a vital dominion

Of the roman empire.

Arya: When we talk about the roman empire,

Sometimes people are surprised to learn

That the entire strip of north africa

Was part of that roman expanse.

Birley: North africa was a hugely significant part of rome.

It was the main bread winner

For a very, very large part of the empire.

Narrator: Tunisia lies hundreds of miles

Across the mediterranean from the heart of the realm,

But its fertile lands were crucial

In feeding rome's almighty army.

And as the empire grew, tunisia flourished,

Its vast new wealth funding lavish examples

Of roman architecture,

Including a 35,000 -seat amphitheater

Modeled on rome's colosseum.

Arya: This, more than anything else maybe,

Was saying rome is here.

And when you make it this big,

It's a really massive statement.

(crowd roaring)

Narrator: But 100 miles north of the amphitheater,

One roman settlement in tunisia

Has perplexed archeologists for centuries.

On the outskirts of the coastal town of nabeul

Sit mysterious high -status roman villas.

Ancient records reveal this was the location

Of a prominent city called neapolis.

(dramatic orchestral music)

And it was deemed so significant,

It may have been declared an official roman metropolis

By julius ceasar.

But the archeology is an enigma.

The ruins here are nowhere near big enough

To match the bustling city history seems to record.

(ocean waves crashing)

So, where is the rest of it?

And why has it vanished?

The answers to these questions would remain a mystery,

Until now.

Because an incredible chance discovery

Has revealed one of the greatest forgotten cities

Of the roman empire.

(gentle orchestral music)

The history and fate of neapolis

Has intrigued archeologists for hundreds of years

Because ancient documents reveal next to nothing

On how this once thriving roman city gained its importance.

Lowe: Like so many cities, it doesn't feature

In the history of the empire.

The written sources focus on what's going on in rome,

They don't recount what's happening in the provinces.

And so neapolis disappears.

Narrator: But the archeology on land

Reveals an elite social class at the heart of neapolis

That rivaled even rome's.

(dramatic orchestral music)

Some of the most striking evidence

Is now kept at the nabeul museum,

Including a series of elaborate and expensive mosaics,

All recovered from just one villa.

Arya: There's so many of these mosaics in one single house.

The owner had sophisticated taste, was wealthy,

And was able to commission great works of art,

In this case in the form of mosaics,

That rivaled those anywhere in the roman empire.

Narrator: It seems some of neapolis's inhabitants

Became very rich (man laughing)

And took pride in flaunting it.

And for dr. Darius arya, the most striking example

Is a square mosaic found in the villa's dining room.

Arya: You've got these two roosters

Dropping gold coins into this jar,

And so much so that it's filled up and it's spilling out.

The owner of the house, he's saying to his guests,

"look at this, I'm really successful,

"so much so that the coins are just spilling out of this jar

"and on to the ground, I'm more successful than you are."

Narrator: So what could have been the source

Of such extreme wealth?

And could it unlock the secrets

Of neapolis' seeming importance?

For the past 15 years, archeologist dr. Mounir fantar

Has attempted to solve this mystery.

(fantar speaks in foreign language)

(ocean waves crashing)

Narrator: The few records of neapolis that do exist

Mention the city had a commercial port.

But fantar had failed to find any evidence of it

In the site's archeology.

(fantar speaks in foreign language)

Narrator: It took a massive storm

To finally give fantar his answer.

(thunder booming)

In 2013, heavy winds hit the southern mediterranean,

Ravaging the seabed off the coast of nabeul.

(gentle orchestral music)

Days later, strange stone shapes

Began to emerge from the sea floor,

Shapes that appeared unnaturally straight.

Further investigations revealed something startling.

They were remains of a roman settlement.

Stone blocks, columns, and foundations.

(fantar speaks in foreign language)

Narrator: Could these remains

Be the missing harbor front of neapolis

Fantar had been searching for?

To find out, he and his team

Took their investigation to the sky.

Using drone imagery, they built up a full view from above

Of the ruins on land and underwater,

And it revealed something astounding.

(drone buzzing)

(mysterious music)

The remains in the sea lined up with those on the shore.

For fantar, this could only mean one thing.

(gentle orchestral music)

They must have belonged to the same roman settlement.

It was a discovery that stunned archeologists.

Arya: How about rediscovering half of a city?

So to connect what we have on the land

With what is under the sea, that's unbelievable.

(dramatic orchestral music)

Narrator: Now, after years of underwater investigation,

Fantar's team has mapped out

A complex of buildings, streets,

And a large industrial site.

The remains of neapolis have grown from a suburban community

To a vast urban layout.

And these newly-discovered submerged ruins

Could finally unlock the mystery of neapolis' importance.

Because they seem to include

What fantar had spent years searching for:

Ruins of a harbor, just as the historical records suggested,

Large enough to make it a major hub for international trade.

(fantar speaks in foreign language)

Narrator: On land and underwater,

The ruins of neapolis now bear all the hallmarks

Of a major roman port.

But what was the secret of the city's success?

And what ultimately destroyed it?

(water gurgling)

The discovery of sunken roman streets, buildings,

And a massive harbor off the coast of tunisia

Has stunned archeologists.

The submerged remains, together with ruins on land,

Are evidence this was once

The powerful roman port city of neapolis.

Now experts are trying to piece together

How neapolis earned its wealth and power.

They suspect some of the city's fortunes

Came from the lush tunisian produce

That fed the roman empire.

Arya: When we think of north africa today,

We think of dryness, heat.

Back in the day, it was a lot more humid,

A fertile breadbasket area that would have supplied grain

And other agricultural products

To rome and the rest of the empire.

Narrator: Set on the coast, neapolis was perfectly sited

To export food from tunisia's interior

To roman ports across the mediterranean.

Arya: It's about location, location, location.

With supply and demand,

Neapolis is going to grow and flourish and expand.

Narrator: But dr. Mounir fantar believes

Neapolis earned much of its wealth and status

From something else,

Something everyone wanted across the roman empire.

And a clue can be found among the ruins on dry land:

An intricately decorated ceramic basin.

(fantar speaks in foreign language)

Narrator: For fantar, this depiction of the god oceanus

Reveals the coastal city flourished

Thanks to the bountiful stocks of fish in the mediterranean.

But there's no evidence that neapolis made its fortune

By catching and exporting fresh sea food.

In fact, the archeological site

Reveals only their rotting remains,

Laid out in a collection of stone tanks.

(fantar speaks in foreign language)

Narrator: Fantar believes these tanks

And the rotting fish inside were the secret to success

Because they were used to make a fish sauce called garum.

(gentle music) (liquid dripping)

Garum became the condiment of choice across the empire,

Used for cooking and enjoyed as a garnish.

It was the quintessential roman ingredient.

Birley: Garum is just a fundamental part

Of the roman diet.

And anybody who would require it as part of their food,

It's something they're used to,

It's a flavor which they enjoy.

Lowe: Garum is found everywhere in every house

Regardless of wealth.

Everybody is eating this.

This is the ketchup of the roman world.

Narrator: But what made this fish sauce so special?

The secrets of why romans consumed so much of it

Have remained elusive

Because it had been thought the original recipe for garum

Had been lost to time.

But now it's being resurrected,

Thanks to an incredible discovery

In one of ancient rome's most fascinating lost cities:

Pompeii.

(dramatic orchestral music) (volcano booming)

In 79 ad, the eruption of mount vesuvius

Buried the city under 20 feet of ash and volcanic rock.

(ash crackling)

But this thick layer also acted as a preservative,

Slowing down the decay of organic material.

In 2014, professor dario bernal-casasola

And his team from the university of cadiz

Began excavating at pompeii

In search of garum, frozen in time.

Bernal-casasola: Pompeii has an extraordinary

State of preservation of the remains

That normally we can't find in other archeological sites,

And we wanted to find organic residues of garum.

(gentle orchestral music)

Narrator: In an incredible stroke of luck,

The team found a garum store,

And inside were 2,000-year-old traces of the sauce itself.

Now, for the first time ever,

An actual sample of garum could be analyzed

To find out exactly what it was made of.

The team joined forces

With experimental scientist dr. Victor palacios.

(palacios speaks in foreign language)

(bernal-casasolas speaks in foreign language)

Narrator: Through microscopic analysis,

The team found pollen grains,

Revealing a selection of herbs were used in pompeii

To flavor the sauce.

(palacios speaks in foreign language)

Narrator: The team believes garum was made

With varying combinations of herbs and fish,

Depending on local tastes.

And the sample told them exactly which species of fish

Was used in this pompeiian recipe.

Bernal-casasola: The remains has allowed us to study the bones

In order to know the species that they were using.

We know it was being produced with anchovies.

Narrator: But the team found one part of the fish

Was key to the whole concoction: Its intestines.

These have enzymes

That literally digest the protein in the fish muscle,

Turning it into liquid.

Archeologists have found ancient garum-making tanks

Across the roman world,

All with a similar design and engineering

To the tanks uncovered at neapolis.

Dead fish were left to ferment with salt

In the higher tanks, and as they did,

The pipes drained the resulting liquid

Into the lower reservoir,

Capturing the juice which would become the final product.

The large quantities of salt used in the fermenting process

Meant the sauce would keep for years.

(gentle dramatic music)

The result was a tasty protein-packed shake

That provided much needed nutrients

To the mainly cereal -based roman diet.

Lowe: Imagine you are primarily eating grain-based porridge.

Garum is probably the principal source of protein.

Narrator: In the land-based ruins of neapolis,

Experts counted around 100 garum-making tanks,

Suggesting a substantial scale of garum production.

But in the underwater remains,

Divers found something extraordinary.

(diver gurgling)

There were at least another 100 tanks

Hidden beneath the waves.

It's a discovery that reveals

Why there was such a large commercial port here.

Neapolis was actually the epicenter

For the mass production of fish sauce.

(fantar speaks in foreign language)

Narrator: For mounir fantar,

It's conclusive evidence neapolis made its fortune

Through producing and exporting garum

On a scale unrivaled in the rest of the empire.

But how did its producers in neapolis,

On the southern boundary of the vast roman world,

Manage to reach markets thousands of miles away?

The answer can be found on the opposite edge of the empire,

In a unique collection of documents suggesting neapolis

Was part of the ancient world's greatest supply chain,

One that would power the roman military machine

As it conquered over two-million-square miles.

(dramatic orchestral music)

Off the mediterranean coast of tunisia,

Archeologists have made an incredible discovery.

The submerged remains of an ancient harbor

Confirm this was once home

To a crucial commercial hub for the roman world.

The city of neapolis.

Here, they produced and exported

Vast quantities of a fish sauce called garum,

And it became the ultimate must-have condiment

In an empire that covered almost two-million-square miles,

From the north african coast

To the furthest reaches of England,

Almost 2,000 miles from neapolis.

Birley: So we're at the very northern part

Of the roman empire,

On the border, the frontier of the empire.

Narrator: Around the early 2nd century ad,

The largest roman army in the entire empire

Was stationed here on hadrian's wall,

Struggling to keep hold of its newly occupied territory.

Birley: The british really didn't wanna be conquered.

So over 30,000 soldiers and their families and communities

Were stationed permanently in roman britain.

(tools clinking)

Narrator: For the past 13 years,

Dr. Andrew birley has supervised investigations

At vindolanda fort.

Birley: Liz, that's looking wonderful.

Narrator: One of 16 heavily defended garrisons

That ran the length of hadrian's wall.

And he's found evidence it was manned by soldiers

From across the empire.

Birley: You'd get people from syria,

North africa, Spain, Italy, France,

Coming to this part of the world for one effort,

One big military effort.

Narrator: Among vindolanda's many treasures,

Archeologists have uncovered around 500 letters

Sent to and from roman troops based at the fort.

And many contain requests for favorite foods from back home.

Birley: You've come to a completely different

Alien environment,

One of the ways that you can feel comfortable, of course,

Is having that taste from home.

Narrator: The finds have revealed

That even here on this faraway frontier

Soldiers were being sent a variety of goods

From their home countries.

Birley: We find little african drinking cups,

We find couscous pots.

I mean, couscous hasn't been locally available

For about 1,900 years.

Narrator: And among the most sought-after products

Was garum.

Birley: Garum is just a fundamental part

Of the roman diet,

Particularly the mediterranean diet,

And anybody who's come from that part of the world

Would require it as part of their food.

Narrator: Records have revealed the popularity of garum

Across the empire.

And the newly discovered remains off the tunisian coast

Reveal neapolis became the realm's biggest producer

Of this essential roman food.

But the city sat on the southern boundary

Of the roman world,

Hundreds if not thousands of miles

From many of its would-be customers.

Fortunately for the city's garum-makers,

Neapolis was part of one of the greatest supply chains

The world had ever seen.

Birley: They've got something called

The military annona system.

(ship crackling)

Imagine just a giant conveyor belt

Which starts in the core of the empire in the mediterranean,

It winds itself around like a snake all the way to the edge.

Narrator: The romans invented a mass distribution system,

Picking up and dropping off goods in bulk

And transporting them from the very heart of the empire

All the way to its outskirts and back again.

Birley: You could ask for practically

Anything that you'd want

From any part of the empire

And some warehouse not too far away from you

Would have it there for you.

(dramatic orchestral music)

Narrator: Experts believe the garum producers of neapolis

Tapped into this giant trade network.

At the national museum of denmark,

Dr. Athena trakadas has been studying

The production and distribution of ancient fish sauces.

She believes it's possible to find out

Where neapolis's garum went

By tracking down its amphora,

The ceramic jugs it was packaged in.

Trakadas: Amphora are very useful

Because not only are they durable,

The shape of an amphora lets an archeologist know

Where it was manufactured.

It's very distinct,

It's like the coca cola bottle of antiquity.

Narrator: Neapolis' amphora are clearly recognizable

By their shape and insignia.

Dr. Trakadas thinks it's possible

To map out the product's movements

Thanks to one surprising type of archeological evidence:

Shipwrecks.

(water gurgling)

Trakadas: With a shipwreck you have a time capsule.

For archeologists, it's advantageous

Because you can really get a sense of commerce.

So you know at one point in time

What things were going where and when.

Narrator: The discovery of roman shipwrecks

Has been the key to knowing

Where neapolis products were headed

And what route they were taking.

(dramatic orchestral music)

Trakadas: We see them along the west coast of Italy,

In southern gal, what is now France,

Into the iberian peninsula, as well as western north africa,

So a wide distribution throughout

The western mediterranean.

Narrator: This vast distribution

Went far beyond the shores of tunisia.

It's evidence neapolis mass produced a quality sauce

That was in extremely high demand,

Propelling it to the very pinnacle

Of its wealth and influence by the 2nd century ad.

But the city's success would be short-lived.

(thunder roars)

An apocalyptic storm was gathering

Both for rome and for neapolis,

And the capital of garum would soon succumb to the sea.

(waves crashing)

(thunder booming)

A powerful storm off the coast of tunisia

Has exposed the underwater ruins

Of a vast section of the roman city of neapolis.

Its discovery has revealed neapolis was once a thriving hub

On the empire's trading routes

And the roman world's largest producer of garum,

A fish sauce that was an essential

Part of the roman diet.

But neapolis then disappeared from history.

And today, the majority of its industrial heartland

Lies submerged by the mediterranean.

(dramatic orchestral music)

But why did it sink below the waves?

(thunder roars)

A force of nature revealed this part of neapolis,

So could something similar have destroyed it?

(ocean waves crashing) (gentle orchestral music)

Earth scientist dr. Chris jackson has been investigating

If a natural disaster hit the mediterranean

Around the time neapolis disappeared from history,

And he's discovered the area

Has always been prone to catastrophic events.

Jackson: The mediterranean would be a beautiful place to live

But it's also potentially a very dangerous place.

We have an area of very active tectonics,

So this is where the plates are moving past each other,

(earth rumbling)

And that means this area is prone to earthquakes.

And if you have earthquakes,

You also have the potential for giant landslides.

(rocks thudding)

And then on top of that,

Because we have plates going beneath other plates,

We also can generate giant volcanoes as well.

(volcano booms)

Narrator: A massive earthquake close to neapolis

Would have the potential to destroy the coastline.

But there are no historical records

Of quakes in this part of the mediterranean

At the time part of the city disappeared.

Jackson: We know that this region,

Although it was subject to very small earthquakes,

It wasn't subjected to the big earthquakes

Which can cause cities to crumble to the ground.

(ocean waves crashing)

Narrator: Another theory that may explain

Why the harbor front is now underwater

Is an increase in the level of the mediterranean.

Jackson: The rise of sea level could have just flooded

Half of the city,

But we know that over this time period

Sea level has not risen by enough to be the cause.

Narrator: So if it wasn't an earthquake,

Landslide, volcano, or rise in water levels

That submerged part of neapolis, what did?

(dramatic orchestral music)

Dr. Darius arya believes there is a clue

In a catastrophic event

That happened 1,200 miles away from neapolis

In alexandria, egypt.

It's here that roman historian ammianus marcellinus

Recorded a cataclysmic natural disaster

Hitting the egyptian city in 365 ad,

(water gurgling)

Submerging many of its finest buildings.

Arya: "the solidity of the earth was made to shake

"and the sea was driven away.

"the waters returning when least expected

"killed many thousands by drowning.

"huge ships perched on the roofs of houses

"hurled miles from the shore."

Narrator: For dr. Arya, this description

Of a massive wall of water hitting the land

And destroying everything in its path

Can be only one thing.

(dramatic orchestral music)

Arya: He's describing a tsunami.

Narrator: A tsunami so deadly and powerful

It completely engulfed alexandria.

If the account is true,

Could it also have annihilated part of neapolis?

Dr. Jackson believes there may be a link.

Jackson: Tsunamis are often triggered during earthquakes

That push the water up into the air,

And as the water collum collapses,

That is the tsunami wave rippling

And pushing away from the epicenter of the earthquake.

Narrator: So could an earthquake

Somewhere in the mediterranean have caused a tsunami so big

It swamped alexandria and neapolis?

(door squeaking) (door rattling)

To find out, dr. Alina polonia and her team

At the italian national research council

Gathered dozens of core samples from the seabed.

Polonia: This sample, which is about seven meters long,

Is part of a sediment core

That we collected in the eastern mediterranean.

Narrator: This sample is a snapshot

Of how the sea gradually laid down layers of sediment

Over 10,000 years.

Polonia: The sedimentation rate for this deposit is very low,

It's 0.1 millimeter per year.

That means that one centimeter represents

100 years of sedimentation.

Narrator: But one section of the core

Revealed a layer of sediment

Unlike anything the team had ever seen before.

Polonia: This point to this point have, more or less,

Two meters of sediments that were deposited instantaneously,

And I mean, in hours.

Narrator: Normally, a century's worth of sediment

Is less than 1/2 an inch thick.

But this massive layer of sludge

Was dumped on the sea floor almost instantly.

In some parts of the mediterranean,

The team estimates it was up to 82-feet thick,

Over a billion times larger than normal.

Polonia: This type of deposits,

The triggering mechanism responsible

Is very peculiar and very rare.

(dramatic orchestral music) (water gurgling)

Narrator: This huge dump of sludge

Could only have come from a massive upsurge of water

Dragging sediment from the bottom of the sea

And dumping it elsewhere.

To the team, it is evidence of a mega tsunami

Of unparalleled size and strength.

(gentle orchestral music)

Carbon dating revealed when it happened.

Polonia: We have found an age for this deposit

That is in good agreement with the 4th century ad.

Narrator: The date of the mega-tsunami is a match

For the historical account of the destruction of alexandria

In 365 ad.

But what triggered it?

The team traced the source of the huge dump of sediment

To an area just off the coast of crete.

They now believe this was the epicenter

Of a massive ancient seismic event.

Polonia: It was possible to define

The magnitude of this earthquake,

Which is 8.3 to 8.5, so it's a very large earthquake.

(ocean waves crashing)

Narrator: 8.5 on the richter scale is almost as strong

As the quake that sparked the 2004 indian ocean tsunami,

Which spread over 3,000 miles from its epicenter,

Killing nearly 1/4 of a million people.

(water whooshing)

(gentle orchestral music)

It means the sheer force of the 365 quake

Was powerful enough to trigger a deadly tsunami

That not only hit alexandria,

It also struck neapolis.

Polonia: We are dealing with a very exceptional

And catastrophic event which should have produced

Devastating effects along the coasts.

(water whooshing)

Narrator: The evidence suggests the tsunami

Could have created untold destruction in neapolis,

Perhaps even submerging its harbor.

But for some experts, the sudden death of a prosperous city

Because of a tidal wave doesn't quite ring true.

Because it took a lot to knock out the romans.

The suspicion is backed up by evidence

Life continued in neapolis for centuries after 365 ad.

Arya: Romans were extremely resilient people.

And when their cities were struck

By fires, floods, and earthquakes,

They rebuilt, they shored up monuments, they reconstructed,

They recycled what was able to be salvaged.

They didn't give up very easily.

Narrator: So, what ultimately led neapolis' dwellers

To finally surrender the city to the sea?

Experts now suspect the devastating tsunami

Wasn't the direct cause of neapolis' demise.

But it was the beginning of the end.

(ocean waves crashing)

(dramatic orchestral music)

Experts are piecing together

The story of the lost city of neapolis,

A bustling roman port on the tunisian coast that grew rich

By producing the empire's most essential food:

A fish sauce known as garum.

Today, a large section of neapolis

Lies under the mediterranean.

What could have caused its demise?

Geological evidence suggests the area was hit

By a cataclysmic tsunami in 365 ad.

But archeological finds have revealed that, astonishingly,

The city survived.

Lowe: We know that it continued to prosper

Because we've got inscriptions from the 5th century ad

And we have 6th-7th century burials in neapolis,

So there's occupation still going on.

Narrator: Now, new clues suggest the 365 tsunami

May indeed have caused the end of neapolis,

But in a much more gradual and insidious way.

(water gurgling)

The evidence comes from sediment samples

From the time of the tsunami.

When dr. Alina polonia analyzed the cores

Taken from the deepest depths of the mediterranean,

She was astounded to discover marine plants and organisms

Normally only found in shallow waters.

Polonia: These samples show displaced species

That live in very shallow water,

From zero to 10 meters of water depth,

Transported down to 4,000 meters.

Narrator: These coastal water species

Could never survive in the deep.

So why were their remains found 13,000 feet underwater?

Dr. Polonia believes it's evidence the 365 tsunami

Not only devastated the north african coast,

It also wreaked havoc under the sea.

Polonia: The tsunami reaching regions with shallow water

Amplified its wave.

The wave drained material from the coast

And transported it backwards in the ocean.

Narrator: As the tsunami hit the shore,

It churned up the coastal shallow waters

And dragged their contents back into the abyss

In a giant underwater landslide.

As the sediment was sucked away from the scoured coastline,

It left behind countless tiny spaces and gaps

Amongst the coast's remaining earth and sand.

Earth scientist dr. Chris jackson

Believes the underwater landslide

Would have completely destabilized

The ground neapolis was built on.

Any further earth tremors would push the city's water table

Into the gaps created by the displaced sediment,

Turning the shore into a soaking bed of sand and silt

In a phenomemon known as liquefaction.

Jackson: Most people would be familiar with liquefaction

From being on the beach

When they stamp up and down on wet sand

And they sink down into the earth.

Narrator: Sinking into sand on a beach

May be harmless for a vacationer.

But, as dr. Jackson demonstrates,

For a city, it can be deadly.

Jackson: What I've got in my hand here is a building.

It's actually a brick.

But you can see if we put it down onto the sand

We can see it kind of settles in.

Even with a bit of gentle pushing it's not sinking at all.

Narrator: The ground above the waterlogged sand

Appears firm enough to support

The weight of the heavy building.

But just like the earthquake-prone tunisian coast,

This ground's stability is undermined

If the terrain is hit by a tremor.

Jackson: So here I am with my earthquake,

And I'm just gonna gently tap the side of this.

(hammer thudding)

Narrator: As the tremors shake the saturated ground,

Water is forced up through the gaps in the sand.

Jackson: Wow, and all of a sudden you can see the water

Pooling on the top surface and bubbles all over the top.

(hammer thudding)

Narrator: The water pushes the sand apart,

Reducing its structural stability.

Jackson: Now half of the brick has sunk down into the sand

And is lost forever.

When the ground is shaken, the sand grains can't compact,

So we go from having sand

To actually water with sand grains floating in it.

Just imagine if this brick was a house.

(water gurgling)

Narrator: Dr. Jackson believes

That the massive tsunami

May not have submerged neapolis' harbor,

But it weakened the ground underneath it.

Any subsequent tremors would have caused

The now destabilized coastline

To start sinking into the sea.

(gentle orchestral music)

And geological evidence suggests

That in the centuries that followed the 365 disaster

Tunisia suffered a barrage of small-scale earthquakes.

Jackson: The cumulative effect of those small earthquakes

Could be to really, really damage the infrastructure

In one particularly location.

(earth rumbling)

Narrator: It seems the 365 tsunami

Set off a slow and painful death for neapolis.

And in the decades and centuries after it,

Every small quake caused the city

To sink further and further into the mediterranean.

But according to historians,

This wasn't the only reason for the city's decline.

(feet stumping)

The western roman empire was also weakening,

The result of a series of invasions.

In 476 ad, it finally disintegrated,

And its vast trade network ground to a halt.

Just over a 100 years after the devastating tsunami,

Neapolis was on its own.

Lowe: Once the ability of the roman empire

To keep the sea lanes open breaks down,

The bottom falls out of international trade

And the world shrinks.

(pebbles crackling)

Narrator: As the fortunes of rome faded,

The trade network that fed the romans' demand for garum

Also began to falter.

Birley: As that starts to dissolve,

Your market starts to disappear.

And suddenly, what was a really sustainable good business

Starts to look very shaky on its foundations.

That story was repeated not just in north africa

But right around the mediterranean provinces

And other provinces of ancient rome.

Narrator: Dwindling demand, a disrupted supply chain,

And an industrial complex slowly sinking

Into the waters of the mediterranean

Meant neapolis's fate was sealed.

The city and its tanks were abandoned.

Arya: When we look at the history of neapolis,

Its rise and eventual decline,

It really does parallel with the history of rome.

When that tapers off,

Then the fortunes of neapolis are gonna taper off.

(dramatic orchestral music)

Narrator: The city of neapolis grew rich

On a humble fish sauce

That became an international statement of roman identity.

Its wealth and importance

Allowed it to survive a mega tsunami,

But it could never recover from the convulsions

Sweeping across the ailing empire.

As the remains of the harbor sank beneath the waves,

Neapolis slipped from memory.

But now its stunning re-discovery

Reveals how this lost city's spectacular rise and fall

Echoes the fortunes of the entire roman empire.