- [Narrator] For thousands of years, the Adriatic Sea has guided ships into the safe harbors of Croatia's Dalmatian coast.

Among these ancient ports stands Zadar, one of the country's oldest continually inhabited cities.

Colonized by the Romans in the 1st century BC, remnants of the Empire's occupation endure to this day.

- [Mladen] The Romans and Greeks before them, the people who built foundations, let's when you see what they used, what they did, it's not changed eventually too much today.

The main square stands in the same position where the Roman main square was.

The main raster of the streets in Zadar is following the streets that we had in Roman times.

So we are living in the same place where Romans lived in these first centuries 2,000 years ago.

- [Narrator] The 1st and 2nd centuries marked the golden age of the Roman Empire.

Every artifact uncovered by archeologists and preserved by conservators tells a story.

A glass jar bears the stamp of its creator.

A ceramic amphora reveals its city of origin through shape and design.

And ancient coins, marked with the heads of emperors, disclose their age.

As they colonized existing settlements like Zadar, the Romans also constructed elaborate country farms, or villas, whose valuable products like olives and wine helped sustain and grow the Empire.

- [Luka] All these products needed to be transferred either to Italy or other provinces, so the transport was, in fact, the ships which were carrying all this stuff.

It was much cheaper than transferring along the inland roads.

- [Narrator] As these Roman ships sailed from colonies along Croatia's Adriatic coast to ports across the Mediterranean and beyond, they left their archeological footprint across the sea floor.

(soft music) For over a decade, underwater archeologists and conservators at the International Centre for Underwater Archeology in Zadar, or ICUA, have perfected their expertise in uncovering and meticulously documenting the traces of this rich history.

- [Luka] We have a lot of abundant cultural heritage underwater in Croatia.

And the main reason for our center is in fact the protection of it.

- [Narrator] During recent excavations of an ancient Roman harbor near Zadar, the team at ICUA made a remarkable discovery: the wooden remains of a Roman ship dating to the 1st century, AD.

- [Roko] You know that feeling when you find something that is really valuable to you.

And then that feeling overwhelms you.

So that's basically the feeling that we get while excavating, and then when you find something, for oh my god, this is 2,000 years old, so I'm the first one, the first person who gets a chance to view this object after 2,000 years, so the last one who viewed it, it was a Roman citizen.

So that's beautiful.

- [Maja] When you are the first one to see the ship remains, after 2,000 years, that's a very special and personal, emotional moment, so things like this always surprise you.

- [Narrator] This find marks the beginning of a comprehensive archeological process that will span years, if not decades.

How do archeologists and conservators document and preserve this sunken history?

And what hidden stories still lie submerged, waiting to be discovered?

(uplifting music) - [Announcer] Major funding for this program was provided by The Batchelor Foundation encouraging people to preserve and protect America's underwater resources.

Additional funding was provided by Trish and Dan Bell and by The Parrot Family Endowment for Environmental Education.

- [Narrator] On the north end of Old Town Zadar, underwater archeologists at the International Centre for Underwater Archeology prepare for another day of excavation field work.

As a UNESCO-supported center working with world heritage underwater, ICUA is the only research institute of its kind in the world.

- [Mladen] So, we are underwater archeologists and conservators of underwater archeological material, and our main tasks are scientific research of underwater archeological sites, education of the students, and presentation to the wider public.

- [Narrator] ICUA's experts collaborate with researchers worldwide to conserve underwater heritage at least a century old, spanning from the prehistoric period to the First World War.

- [Luka] The conservation work is very important aspect of our center, and this is the biggest facility that we have in Croatia for underwater cultural heritage.

The Adriatic Sea has a lot of salts.

So getting this salt out of the material is a priority in conservation.

Otherwise, all of these objects will collapse, and they will be destroyed in 10 years, let's say.

- [Narrator] The center is also developing a specialized library and constructing a new museum space, both dedicated to the field of underwater archeology.

As an educational center, ICUA provides underwater field work training and experience to archeologists from around the world.

One such project is a unique excavation led by the center's director, Dr. Mladen Peai In 2020, the ICUA team discovered a wooden plank and iron nail buried in the ancient Roman harbor of Barbir.

Subsequent excavations revealed a sunken Roman ship, estimated to be over 40 feet in length.

This rare wooden find has been naturally preserved by layers of silt and sand for over 2,000 years.

- [Mladen] To find the ship in this good condition, it's really not a common find, so basically we were really happy to discover it was protected in such a good condition.

This is something that we will leave, we will start this year, document as much as we can, and we will leave this for the next year also.

We are continuing the excavation this year, and the idea is to uncover only a small part of the ship in order to overlap the pictures and the plans that we are going to make this year.

(inspiring music) - [Narrator] Today, the abandoned Roman harbor at Barbir lies submerged in shallow waters due to centuries of erosion, settling, and sea-level rise.

- [Mladen] The harbor is made from two parts, let's say.

One part is much bigger.

It is the pier that we see underwater.

Today it is possible to see different small stones that were part of the harbor and also big blocks of the stone more than two meters long that were meant to protect the inner part of the harbor from the big waves that are coming.

- [Maja] So probably the harbor existed because of the Roman villa on the coast.

It was their harbor to transport goods along the coast or outside of Adriatic.

We don't know.

But we know that there is a lot of harbor material, so a lot of imported products from all over the Roman Empire.

- [Narrator] To dig trenches for this year's excavations, the team secures a metal grid over the site, then prepares to remove sediment from the seafloor.

- So for excavation in underwater archeology, we use water dredges.

So the dredges that have a suction power, and they actually help us like a vacuum cleaner.

They help us to clean the sediment.

Then we are excavating layer by layer.

So we are excavating one layer, and the layer tells us a story about the period in which it formed.

And then there is another layer underneath it, which is older.

It's called archeological stratigraphy.

- [Narrator] Facing uncertainty about what lies beneath, the team must be vigilant in spotting fragile artifacts before they are harmed.

After an artifact's resting location is precisely measured, it's assigned a unique identifier, photographed, and placed in a secure net bag.

- According to analysis of them, we can tell from which period they are.

So basically we know that although this ship sank somewhere in the we know that the harbor existed even after the ship.

Most of the material on the surface comes from the 5th century AD.

So during excavations, we found first elements, small pottery, from the 5th century.

Then if you're going lower, then you can see the elements from 4th century, 3rd century.

And eventually when you come close to the ship, you can see the pottery and small finds, which are dated to the same era when the ship sank.

So basically, we are cutting the layers and reconstructing them.

It helps us to see when the ship sank, but also to see how the harbor existed and how rich the harbor was in different periods of the time of the existence.

(soft piano music) - [Narrator] Back at ICUA, these unique and ancient finds undergo thorough documentation, including photography and detailed record-keeping in an excavation diary.

They also must be kept submerged in seawater until they can be properly conserved.

Long-term exposure to open air would damage them irreparably.

- So, each element, each artifact that comes from the water has to pass a long process of desalinization.

This process is where the elements or the artifacts are put in the tap water in order to extract all the salts that are inside of the structure of this artifact.

Otherwise, if you just take it out from the water and leave it to dry, it'll break.

It'll completely be destroyed in a really short time.

- [Narrator] Each of ICUA's conservators specializes in processing specific artifact materials, including metal, glass, wood, and ceramics, such as this amphora from another underwater These vase-like jars were used for transport and storage by the Greeks and Romans.

- During all the process of conservation, we are really careful because these pieces have really historic and archeological value.

And we need to respect our history, our heritage.

You know that somebody in the history made this and you respect the work of this person.

Sometimes you find the prints, like the finger of the pottery maker.

For me, it's really fantastic to see.

It's like some kind of the personality of the person who made it like thousand years before.

- From ceramics we also can tell different things, so basically we can tell from which period the ceramics is.

It is even possible to tell from which workshop in Roman time this pottery was done.

- [Narrator] After a year-long process of desalinization, these finds from the previous year's excavation are now able to be more closely examined.

- [Mladen] For the pottery shards, we have them from different parts of the Mediterranean.

For example, maybe most interesting are the ones from North Africa that come from 4th and 5th century that was decorated by different stamps on them.

We also have some pottery that was used by the Romans in this area during their normal everyday life.

But we have some pottery also that comes from hinterland, from the inner parts.

And so this pottery came not by the sea trade probably and this gives us some clues that the trade was not going only in one direction, but it is possible that was the trade that came from the different ships through this port to hinterlands and other way around also.

But maybe most interesting finds are the coins.

Many of them were found in one small area, and we can presume that some Roman lost his bag with coins that was left there underwater, and we found it, let's say, almost 2,000 years after.

(upbeat music) - [Narrator] After removing all of the sediment and artifacts, the team finally reaches the preserved hull of the Roman ship.

- [Mladen] The ship had no cargo because it was docked in a bay, in a safe place, let's say.

So we don't have a typical cargo, like big amphoras that were stuck inside of the ship.

It was probably carrying the olives and we know this because between the frames on the lower part of the ship, we found lots of small seeds from the olives from the Roman times.

- [Narrator] As part of preparing the ship for documentation, divers must meticulously clean the fragile wooden construction now laid bare to the elements.

- [Mladen] This lower part is in really good condition.

The parts that are close to the surface were eaten by the ship worms and they are destroyed.

So wood that is underwater often gets destroyed, but the parts of the ship that are deeper, let's say, 40-50 centimeters under the sand, they are completely preserved.

And you can still see the cut marks of the tools that Romans used for building the ship.

- [Narrator] Precise cuts are made in specific elements of the wooden hull.

Through carbon dating, these tiny samples will yield valuable information about wood types and ages.

Larger fragments that had broken off prior to the excavation are also retrieved.

They will play a vital role in helping ship construction experts understand how the ship was built.

As with other materials, this wood will require proper conservation to prevent its destruction.

- Wood naturally absorbs water, so as long as the piece of wood is in the wet environment, it will look very well preserved.

But actually, when you touch that piece of wood, you can feel these cavities.

It is actually soft, and it can even get spongy.

So if you take that piece of wood out to dry, water will evaporate, leaving nothing to hold the structure of the wood.

So, you have to preserve it in order to save it.

- Basically, up to now, we know five or six different species of wood that was used for the building of the ship.

So we have oak.

We have pine tree.

We have olive tree.

So we have different species of wood that was used for different elements of the ship construction.

- We know that this ship was constructed in a way, it's called shell first.

So they would first assemble the outer planking, and then they would insert frames inside.

So the most weight, and the structural element of this ship is actually its hull.

- [Narrator] Divers mark these planks with black labels specifying their relative positions and use blue wire to delineate the spaces between them.

These interlocking joints, secured with wooden pegs, are a sturdy construction technique known as mortise and tenon joinery.

Each wooden peg is marked with a white pin, and red pins are used to indicate wider wooden nails that secure the wooden frames.

- [Maja] Once the model is produced, I cannot come back there and check if we missed something because some things are visible only while you are diving.

You can take a thousand photos, but you cannot be in the same context of diving there and thinking about the boat.

You really need to know what you are doing, because it will be documented forever.

- [Mladen] During excavation, we also have to measure each quadrant end, let's say, or each field that we are excavating in order to reconstruct it afterwards to put it in a proper position.

So we are taking GPS positions of the different frames, but also from the ship construction in order to have exact lengths of the ship construction.

- When everything is finished, then there is a crown of the whole excavation actually, and why are we marking everything?

Because of that moment that everything leads to, and that's documentation.

- [Narrator] Roko Suriis responsible for collecting photogrammetry data at the site.

This technique allows him to capture hundreds of two-dimensional images from multiple angles, which are then merged to produce highly-accurate three-dimensional models.

- So, the markings on the ship itself would not have any sense if we didn't document it properly.

When I go inside of the water to make a photogrammetry, I have to be really certain that the water is clear also.

So there should be no disturbance.

That means that even the smallest particles inside of the water between my camera and the site can interfere with the final result.

Most of the time, underwater visibility is bad.

So even if the visibility is, let's say, half of meter, if you are expert in photogrammetry, if then you can get the whole picture.

So, finally, when you are finished with the software, when you're finished with the computer work, you will get the whole picture of the site.

You will not be able to do that underwater.

It's impossible.

- You can also make 3D models, which basically helps us to learn what are the curves of the ship.

And these ship lines help us to uncover what was the original size of the ship, what was the height of the ship, and different elements that today are broken.

But according to this reconstruction, we can basically see how the ship exactly looked like in the past.

- [Narrator] After thoroughly documenting the ship's exposed section, the delicate wooden hull must be re-covered to safeguard it until archeologists can return for future excavations.

- [Mladen] We could not leave it like this because this wood is really fragile.

Since it is in shallow waters, the waves that come here can go up to two meters and basically they can just, in one moment, rip completely the ship out from this position.

So in this way it is protected and nobody can touch it.

- So we put the sand, sandbags, and then we covered everything with geotextile.

We put it in a few layers, just to be sure.

And afterwards, we are using dredges to put all this material that was already excavated from the boat to return it back inside.

If we left it uncovered, there would be a lot of people who are interested in this kind of things.

So if everyone take one small piece as a souvenir, we don't have ship anymore.

- [Mladen] For now, it is protected in situ, on the site where it is.

Of course, our wish would be after we finish the excavation, maybe to lift it up and to exhibit it.

But this is process that takes lots of time, lots of energy, and lots of money.

So this is something that we have to plan properly in order if we want to take it out.

- All of these finds underwater are treasures.

And we want to keep them where they are until we have a means to really reconstruct them and preserve them.

All those objects can tell us a lot about the history.

- It is very important because if anything happens, these documentations are the only evidence that it existed.

In my opinion, but I'm an archeologist, it is very important to have this connection with the past in order to have a bright future.

So we are also personally and emotionally connected with this.

Documentation is just one part of the process.

- [Narrator] Four years after their discovery of the Roman ship at Barbir, the team at ICUA remains committed to preserving the history found in this rare and unique cultural heritage site.

- What lies in front of us is uncovering the whole ship.

So basically we will not stop.

If it takes us 5 years more, we will take 5 years to completely excavate it.

And then we will be sure that we didn't miss any information that is hidden underneath the layers.

Because the final product of this whole excavation is the story of what happened, why did it happen there, and all the different aspects of the story.

- Archeology is just like any other science.

You get a lot of answers on your questions, but you always raise some new questions.

We are not the first archeologists working here.

Our generation is one of the many, many generations of archeologists who are working on the same problems.

And we are not the last archeologist here.

(soft music) - [Announcer] Major funding for this program was provided by The Batchelor Foundation encouraging people to preserve and protect America's underwater resources.

Additional funding was provided by Trish and Dan Bell and by The Parrot Family Endowment for Environmental Education.

(upbeat music)