Original subtitles

The Roman settlement of Baiae

was the Las Vegas of the Roman Empire -

a place where the rich and powerful came to relax,

party and carry out illicit affairs.

Lured by Baiae's volcanic hot springs, the Romans built

opulent villas and baths here on the Gulf of Naples.

Today, it is still famed for its precious marbles,

mosaics and sculptures.

The ancient authors wrote a lot about Baiae and described Baiae

as a little Rome - as a place for the holiday,

a place grounded with all the aristocracy,

but also with young people, with people walking

on the beach, looking to the sea, people drinking wine.

A fun atmosphere.

It sounds like a party town.

Exactly.

LAUGHTER.

But over several centuries the city slowly sunk

beneath the sea.

Burning.

This area?

More dangerous than...there.

I wish you told me that when we were over there.

Why are you telling me that when we're here?

The underwater site is a treasure trove of mosaics

and marbles dating back 2,000 years.

But today they are at risk.

Now a team of archaeologists and engineers are developing

some surprising new technologies to protect

the underwater site for future generations.

We know Baiae as the underwater city.

Baiae is not an underwater city, it is kilometres

of the ancient waterfront that is now underwater

because of a sudden change of the sea level.

You can see underwater the remains of actual

the villas, also the remains of marbles, streets, shops.

Is there anything else like that in the world?

I don't think that you can find other underwater archaeological

sites in the world like Baiae.

Baiae, on the Gulf of Naples, is one of the most

extraordinary ancient sites in Italy.

The Romans came here for the same reasons we do -

the sparkling Mediterranean, the balmy weather, the lush

vegetation and vineyards.

They were also drawn to the area's thermal springs -

the result of course, of the volcanic activity

beneath their feet.

As the Roman Republic lapsed into Empire, Baiae's

reputation only grew.

In AD 39, Caligula built a bridge made up of merchant

ships linked together and then covered with earth from Baiae

to nearby Pozzuoli - three miles long -

and rode over it in a chariot.

And in AD 59, Nero had his mother, Agrippina,

murdered in her villa here.

The later Emperor Hadrian would have a more peaceful end

to his life, dying of natural causes in his Baiae palace

in AD 138.

University of Naples "L'Orientale" archaeologist

Michele Stefanile showed me around.

Baiae was a luxury resort with incredible architectures

connected with the most eminent men of the Late Republic

and the early Imperial times.

The ancient authors wrote a lot about Baiae and they described

Baiae as a Rome - as a place for the holiday,

a place crowded with all the aristocracy,

but also the young people, with people walking

on the beach and looking to the sea, people drinking wine.

A fun atmosphere, it sounds like a party town.

Exactly.

People like Seneca, for example, decided

to have his villa not in Baiae but on a hill

in that direction.

Just to stay a little bit isolated for the...

It was too loud for him?

Exactly.

Too crazy for Seneca.

Exactly.

And when did this whole area disappear?

We know that after the Late Antiquity, this part

of the territory, of the Phlegraean region

was abandoned.

So, how much to the water level rise?

It depends on the part of Baiae, but normally it's

somewhere between four and six metres.

Wow.

It's a big change.

It's a big one.

Yes, a very big change.

That's why you can see underwater, not only

the floors, but also walls.

It's one of the sites in the world with this

concentration of mosaics from the Roman times,

times, underwater.

So, you can ride on the water and read a mystery five

centuries long or six centuries long.

So, tell me what happened.

How did it get submerged?

The history of the change of the sea level in this

territory is connected with the volcanic activity.

Most of us have heard of Mount Vesuvius, but it turns

out there's another volcanic zone near Naples.

It's burning.

It's more dangerous than...there.

I wish you told me that when we were over there!

Why are you telling me that when we're here?

This area - called Campi Flegrei, or the Phlegraean

Fields - is still active.

It's also why Baiae is now underwater.

The movement of magma underground actually sank

the ancient city's ground level.

Campi Flegrei is one of the 20 known supervolcanoes

on the planet, capable of erupting with a volume

of thousands of times stronger than an average volcano.

Vincenzo tells me that if it were to blow at maximum

capacity today, it would make the AD 79 eruption

of Mount Vesuvius - that destroyed Pompeii -

look like a puppy's sneeze.

Carmine Minopoli is a researcher at the National

Institute of Geophysics and Volcanology.

He walked me through how the monitoring system works,

but before he did, we spoke in one of the stranger places

I've ever done an interview - inside a building that had been

abandoned because of the heat and gases caused

by the volcanic vents beneath it.

All of that volcanic activity remains a risk today.

But it's also what put Baiae underwater 1,500 years ago.

The water has helped preserve the artefacts,

but it can also damage them.

Barbara Davidde, director of the unit of underwater

archaeology at Italy's High Institute for Conservation

and Restoration, has been working at Baiae since 1993.

So, 1,500 years these artefact have been underwater.

What does the sea water do to artefacts over such a long

period of time?

Archaeological remains were protected underwater,

thanks to the sea.

But if they are on the seabed, open, and so not covered

by the sand, they are attacked by marine organisms.

We call bioerosion.

There are sponges and bacteria, also bivalve animals,

organisms, so there is a big variety of bioeroders.

Some statues that are recovered from the sea are completely

destroyed or partially destroyed or sometimes

that we found

that the neck, the head, the hand, is lost.

And all the portion of the statues that are covered

by sand are in good condition.

Concerning the mosaics, for example, we can see some

small holes that don't look so dangerous for the artefacts,

but if we analyse with a microscope these holes,

we will see that inside the tessera, inside the stone,

the hole is not small but it's big, large.

And the monitoring of the site is the solution of this.

At the Archaeological Museum of Campi Flegrei, one piece

of artwork after another shows the damage animals can do.

While it's common to see ancient Roman statues missing

arms or heads, the items in this collection are different.

A veiled woman has been covered with what almost

look like pockmarks.

A base with a dedication to Emperor Hadrian loses

all shape at the top, like a half-melted candle.

This 74cm statue of Zeus on his throne dating

to the first century BC is covered with what looks

like white scrawlings - the remnants of marine

and crustaceans.

But these organisms weren't his only challenge.

The Zeus was likely stolen from the sea by looters.

He wound up in the collection of the J Paul Getty Museum

in Los Angeles, acquired by a curator later indicted

for conspiracy to traffic in illegal antiquities.

He was returned to the Campi Flegrei museum in 2018.

The other sculptures in the museum are now safe

from marine organisms.

But the artefacts that remain below the sea,

including the precious floors that make up the largest

collection of underwater Roman mosaics in the world,

remain at risk.

Finally, it was time for me to go down and see

it for myself.

I was invited to join the team testing new technologies

to help better monitor the erosion, but also to help

the public engage with the site in new ways.

Chiara Petrioli is professor of computer science

at the University of Rome "La Sapienza",

and the interdisciplinary project MUSAS' site

coordinator.

She is behind one of the more ambitious aspects of MUSAS -

its underwater wireless sensor networks.

So, what are the technologies you're testing here this week?

This week, we are testing underwater drones supporting

archaeologists in discovering the site.

We are testing underwater wireless sensor networks that

allow to gather in real-time, data on the conservation status

of the site.

The water quality, the CO2, because here we have very

active volcanic activity and it's important to know

what's happening there.

And also images that we can transmit in real-time,

compressed through novel algorithms from the underwater

environment.

These innovations represent a major change from how things

were done in the past.

They mean that information and pictures about any problems

in the site, like erosion or even looting, can be

communicated much more quickly.

Not only can underwater archaeologists communicate

while they are diving, but we can get data

in real-time about the site, even when archaeologists aren't

there.

So, we have also developed a system for divers.

On the other hand, we are able to localise and we have

developed a way to represent how these underwater cultural

heritage sites were in the past using virtual reality,

so that you can actually have an enhanced experience

visiting the site.

And you can also track in a WhatsApp-like matter

with the rest of the divers and with your beloved ones

on the other side of the planet, and exchange images

or exchange your feelings, even when you are diving.

The way this is being done is through an underwater

Internet.

That's more difficult than it sounds.

Wi-fi, for example, doesn't travel far underwater.

Instead, Petrioli's team came up with the idea

of using acoustics inspired by marine mammals.

So, you have to use a completely different way

of communicating, for very short range, a few metres,

which is short-range in this environment,

you can use wireless optical.

But mostly you have to use the way of communicating

of marine mammals.

So, you need to use acoustic communication.

And this is really challenging because the sea parameters may

change.

The temperature and salinity change.

And this affects the way communication works.

And it's also, you know, a ship passing by, like,

we have right now or water motorbike, this affects

the ability to communicate.

Even the wind rising so that the surface provides

changes, affects the communication, then two devices

are no longer able to communicate.

So, it's very complex, but we came up with an idea.

Let's have mesh networks, like, multi-networks,

and let's use artificial intelligence techniques

to keep changing.

The product we use, the route the information flow has to go

through, the parameters of our communication system.

And we came up with some novel fundamental understanding,

and it works.

What was not possible before is now possible in terms

of performance, transmitting even multimedia information

like images, in terms of real ability of communicating.

And this is a gorgeous application in underwater

cultural heritage, but this is going to change actually

whatever we are able to do in terms of exploring

and understanding these environments across the blue

economy.

Under the water, a whole world opens up.

The sculptures here are replicas.

The real ones are safe above ground in the nearby

archaeological museum.

But the other artefacts, from the walls to mosaics,

are original.

As we swam, statues began to appear out of the water.

This was the nymphaeum of Emperor Claudius,

a place where the first century ruler would have strolled

and admired his sculptures.

I pressed a button on my tablet and held it up.

A 3D version of how the nymphaeum would've looked

appeared on screen.

This is one of the other main goals of MUSAS -

to help divers understand and appreciate the ruins

they're looking at.

But the best was yet to come.

My dive guide, Enzo Maione, stopped on the sea floor

and started to push the sand around.

With each sweep of his hand, more of the mosaic revealed

itself until we were hovering over an intricate pattern

of circles and hexagons.

This was once the floor of a room just off the atrium

of a magnificent villa dating to the second century.

There's nothing quite like seeing ancient

ruins like this.

For one thing, there's the eerie silence of being

underwater - hearing only your own breathing.

For another, there's the intimacy.

Forget the crowds at sites like the Colosseum, down here,

where only scuba divers can go, you can experience this ancient

landscape almost alone.

And knowing that it's being protected for future

generations couldn't be a better feeling.

The team installed the monitoring system at Baiae

permanently in summer 2020.

The project is also being unrolled elsewhere,

including at an ancient underwater site in Puglia.

It's a privilege to see it all in person and to learn how

these innovations could dramatically improve the way

the site is preserved by archaeologists and

experienced by travellers.