The Rise of the Roman Empire (Full Episode) | Drain the Oceans

Where emperors reign and gladiators entertain, sight of luxury, excess, and the ever-present danger of the mob. For five centuries, Rome dominates the Western world. But the real secret of the empire's power lies elsewhere, beneath the seas it once commanded. Without the sea and without controlling the trade routes of the sea, there would have been no empire. Imagine if we could empty the oceans, letting the water drain away to reveal the secrets of the seafloor. Now we can, using accurate data and astonishing technology to bring light once again to a lost world. How does a mysterious lake, miles from the city, explain Rome's mastery of the Mediterranean? It was built on a scale unlike anything else. Only the Roman emperors were this ambitious. What can a maritime graveyard, unearthed in an Italian field, tell us of Rome's one great weakness? And how does a lost marvel on a distant Mediterranean shore explain Rome's greatest ever feat of engineering? The Romans took technology to a whole other level. When the great historian Livy sets out to write the story of his city, he knows it all comes down to location. Gods and men together chose this place, hills with pure air, a convenient river, a sea handy for our needs. All these advantages marked us out for glory. Rome is the world's first superpower. But it doesn't start that way. Over the course of 500 years, it grows from a fortified settlement to a powerful republic, and finally, an empire. Demanding the allegiance of over 16 million people from Britain in the north, down the coast of Africa, and into the Middle East, Rome's power rests on the unrivaled might of its army and engineering skills that astonish its rivals. But that's not all. So everyone thinks they know the story of the Roman Empire. And it's a story of legions, and of roads, and of building massive structures. But the key really was control of the sea. Controlling the seas is essential, because Rome struggles to feed its people. By the first century AD, the population of the capital swells to 1 million, the largest city the world has ever seen. And if those people go hungry, they riot. Well, Rome was dependent on obtaining about 150 to 300 million tons of grain annually to keep the population fed. If you were an emperor, you wanted to be seen as someone who was providing for the population. So really, without that grain coming in, they couldn't hold on to power. How the emperors managed this has long puzzled historians. But now, buried underground and miles inland, an extraordinary discovery could unlock the mystery. Rome's challenge isn't shipping grain from the empire. It's getting it to the city itself. 15 miles from the sea, there must have been a huge port somewhere on the coast, or inland, up the River Tiber. But its whereabouts are a mystery. Today, international teams are trying to piece together the puzzle of the lost port. Archaeologist Peter Campbell is determined to discover how Rome handled its biggest problem. Feeding nearly a million people would have been an incredible task. So the ability to get that material from around the Mediterranean up to the city took just an incredible amount of human willpower and labor. You need anchorage space. You need harbor facilities. Simon Kaye leads a group of experts who are studying the lost port. You need the infrastructure to support them, and you need the administrative framework, indeed, to enable them to function. Clues, first unearthed over a century ago, are tantalizing. The early sources are very, very important. They saw things. They recorded them. Historical texts refer to a port without equal, somewhere on the coast near the mouth of the Tiber. The port of Portus, however, established by the emperor Claudius by 46 AD and extended by the emperor Trajan over 60 years later. The Romans call it Portus, a single carved relief dating from the late second century AD, hints at its magnificence, but gives no sense of its true scale or how it worked. Other sources speak of a hexagonal basin at the center of a vast complex called the Portus Traiani. Could evidence of it still survive 2,000 years later? Simon is convinced that it does, about 15 miles south of Rome, where he's come to investigate strange ruins and a mysterious lake. It has six clearly defined sites and looks man-made. It covers almost 80 acres, as large as 13 Roman coliseums joined together. But there's a problem. It's two miles from the Mediterranean coast. Could the heart of the legendary Portus lie so far inland? And where is the rest of it? So little is known about the layout of the ancient port. It's very, very hard to understand how it all fits together. Archaeologists survey close to the lake. Through here. Then you just get in the different phases running down through there. Probing beneath the surface for any evidence. About a meter, meter and a half or so. Four meters, you start hitting the water table. Combining discoveries made here during past construction work and these new archaeological investigations, it's now possible to produce a new window into the past. The mud and silt of 2,000 years drains away. And six feet below the surface, buried archaeological treasure. The remains, not of a port, but something that might have used it, a boat. From this field, two miles from the coast, four other vessels emerge into the light. It's an extraordinary discovery. The archaeologists pour over the evidence and realize they are some of the most complete Roman vessels ever discovered. It's even possible to date one of them. Based on the construction features, we can estimate that it dates to the second century AD. In the second century, the Roman Empire is at its height. If it ever needed a truly grand port, this is the moment. But if these beautifully preserved boats used this port, why are they so far inland? Peter Campbell finds more evidence. Not far from the wooden boats, the remains of what looks like a long, low wall. And it's definitely Roman. More surveys reveal this is just one section of an early 6,000 foot long structure, now mostly hidden beneath the ground. Further archaeological work unearths a second wall, curling back towards the first. And deposits on the walls give a further clue. If you walk along this structure, you can actually see calcium deposits at a certain level. And it creates this white line along the length of it. And those are actually marine concretions. Marine concretions are sediments that cling to structures at seawater level, leaving a white mark. This whole area, close to the hexagonal basin, was once underwater. It's another astonishing find. In Roman days, this is where the coast was. And the curving structures make up a huge protective harbor. This must be Portus. But one big question remains. The city is 15 miles further inland, connected to the sea by the River Tiber. And the mouth of the river is nearly two miles from Portus. So how did food ever get to Rome? The architects who designed Portus faced one key challenge, feeding Rome's million-strong population. So how does the harbor connect to the city 15 miles away? Moving huge volumes of cargo by existing roads would have been costly. And the most obvious route to Rome, the River Tiber, is too shallow for merchant vessels. Studying the ancient boats dug up nearby, Peter Campbell finds an important clue. Rather than having a V-shape, as you would have with a seagoing ship, this actually has a relatively flat bottom, which would have allowed it to travel in much shallower waters. It was used within the harbor and up the Tiber. This vessel is an important piece of the puzzle in the network that connected the ocean to the city. The harbor lies more than a mile from the banks of the Tiber. How could a cargo-carrying vessel reach the river? Peter consults the archaeological surveys and spots a set of parallel lines near the hexagonal basin. They look like the remains of a man-made channel. The data reveal a major canal system connected Portus Harbor to the Tiber, an astonishing feat of Roman engineering. If you look at the landscape of the river today, there's the main channel that we're in right now. But in the past, there would have been multiple other canals. And we've only recently discovered those others through geoarchaeology. The archaeologists now understand the full scale of the Portus complex and how it connects to Rome. But there is still a mystery. At the heart of the port, beyond the vast main harbor, lies the huge enclosed hexagonal basin, apparently unique in the ancient world. But what was it for? Today, from the surface, it seems like an ordinary lake. But by using the latest computer visualization techniques, we can look deeper. As the water seeps away, it exposes not the muddy banks of a natural lake, but a crumbling brick wall. Similar walls support the other sides of the hexagon. And then something startling, a white block with a hole through the center, one of dozens protruding from the brickwork. Close by, the remains of a column, and just visible on it, Roman symbols for the number 23. Can ruins scattered nearby help reveal the hexagon's purpose? Simon Kay thinks so. To his expert eye, they are Roman and important. I'm currently standing in one of the largest surviving buildings from Portus. The thick walls, large enclosed space, and a wide opening all point to one thing. These are warehouses, warehouses designed to store the most important commodity in the Roman Empire, grain for the people of Rome. They are the largest place of grain storage in the whole Portus complex, making them the largest grain warehouses in the Roman Empire. It's now clear what the drained hexagonal lake is for. Mooring rings for ships to unload, a broad quayside surrounding the lake, and the numbered column docking station, one of dozens in the whole complex. The hexagon is the heart of Portus, a purpose-built facility to manage dozens of cargo ships at a time. Decades of archaeological work haven't simply found some ancient docks and warehouses. They've uncovered the secret to the success of Rome itself, allowing us to understand exactly how the emperors fed a million people. Now, for the first time in almost two millennia, the true scale and brilliance of Portus is revealed in full. Approaching ships arrive at the outer harbor, some more here. Others head further into the port to dock at numbered mooring rings. The great basin can hold over 100 vessels. Surrounding them, another engineering marvel and a hint of the majesty of Rome. Not only warehouses and harbor offices, but giant temples and statues, too. The sheer volume of goods passing through Portus is beyond anything the world has ever seen. While a host of smaller barges wait to ferry cargo through the canals to the River Tiber and onto Rome, the hexagonal basin at Portus is the final crucial link in the supply chain from the empire to Rome itself, the ultimate symbol of Rome's mastery of the seas. In Portus, we're seeing the Roman Empire at its height. We're seeing the first and second centuries AD. They're building a massive port. And it's the most advanced. It's the most monumental. It's the most spectacular port. And it's actually making a statement about Rome. Vessels from across the empire flock to this engineering marvel. Can the surprising cargo of one ship destined for Portus explain how Rome survives one of its greatest ever disasters? The Mediterranean, super highway of the Roman Empire. For five centuries, it's crisscrossed by merchant ships, many carrying grain to Portus. Very few have ever been found. But off the coast of Spain, near the city of Alicante, an ancient shipwreck is discovered by two amateur divers, Jose Bo and Antoine Ferrer. Maritime archaeologists name it after them, the Bo Ferrer. When Carlos de Juan hears about it, he sets out to discover more. We have some evidence of a shipwreck from Roman period right underneath where we are right now. It is absolutely emotional, emotional moment. And I felt that it was the beginning of something. 80 feet below the surface, something rare and precious. The bones of the Bo Ferrer and the remains of her cargo. Carlos thinks it's Roman, but is he right? And what was she carrying? The Mediterranean empties, and light pours once again onto this ancient and mysterious ship. Spread across the seafloor, a mountain of amphorae, many completely intact despite lying at the bottom of the Mediterranean for many centuries. The storage jars are used to carry food, oil, and wine in the ancient world. Clear evidence that this is a Roman wreck. The sheer number of amphorae suggests she was an unusually large cargo ship. But little of her frame remains. Just a few timbers from the hull have survived the ravages of time. It is a great opportunity for the archaeology to learn more about those big vessels, those merchant vessels of Roman period. The fully drained remains reveal a shape that's typical of a Roman merchant ship, but much bigger than most. Pulling her skeleton together from the bottom of the sea, we can recreate the Bo Ferrer as she was on the day she sank. 30 feet wide and almost 100 feet long, she's larger than a tennis court, capable of carrying over 200 tons of cargo. We have other questions, so we have to investigate inside of the shipwreck. So little remains of the ship. Carlos must look to the cargo to learn more. The team raises some of the jars to the surface. Each weighs nearly 140 pounds. On land, they're handled delicately and examined in minute detail. We start to discover some pottery fragments that had waterproof resin inside. Waterproof resin is a key clue. It means the amphorae carried liquid. And in some of them, ancient sediment from that liquid reveals something else, fish bones. The amphorae carry one of the most popular products of the Roman economy, the superfood of the ancient world, fish sauce, known as garum. Well, garum, or fish sauce, is basically a condiment that you would add to food to enhance its flavor, as you would today, as you would do with soy sauce or something like that. And that's because Roman food really was a bit bland. And this is before they had tomatoes, before they had pizza, before they had the things we think of in terms of Italian food. So the Beaufort was carrying fish sauce. But where had it come from? The shape of the amphorae gives Carlos a clue. We knew that that kind of amphoras are related to the fisheries from the south of Spain. But where was the Beaufort taking them? Returning to the drained wreck and removing layers of the amphorae reveals further evidence, a secret cargo hidden for centuries. On either side of the keel, strange metal ingots. The team prizes 22 of them from the wreck. Each weighs 140 pounds. In the laboratory, careful examination of the ingots reveals something unexpected. The hidden cargo is not gold or silver. It's lead. And there's something else. All the ingots found on Beaufort are stamped with the letters IMP. It's the mark of the imperator, the Latin word for emperor. Those marks are telling us that this ingot belongs to the emperor. And that was like, wow. That was just the moment where the Beaufort changed from such a large, big Roman vessel to something absolutely different, a vessel that has been able to link in the story of Rome. The Beaufort isn't just another cargo ship. It's taking at least a ton of metal to the most powerful man in the world. So which emperor could it be destined for? And why does he need a boatload of lead? Off the coast of Spain, a remarkable Roman shipwreck called the Beauferrer conceals a secret cargo, a fortune in lead, possibly destined for the emperor of Rome himself. The drained wreck holds clues that could reveal which emperor. Hidden among the amphorae are two weathered coins. The coins are made of bronze. On one side, a faint image. Almost invisible marks prove the coins were stamped around AD 66, during the reign of one of the most infamous emperors of them all, Nero. The information from the coins allows Carlos to do something even more remarkable. Date the sinking of the Beauferrer to the time of one of Rome's greatest disasters. In 64 AD, an inferno ravages the city for six days. According to legend, Nero plays his fiddle while his capital burns. Whether that's true or not, the huge damage gives him the chance to rebuild the city in his own image. The great fire of Rome destroyed about 2 thirds of the city, and there was a massive rebuilding campaign in the years that followed. And they obviously needed the raw materials to do that. Lead was a very important part of that. Lead lines pipes in all kinds of Roman plumbing, like the luxurious bathhouses enjoyed by the wealthy elite. Carlos believes the emperor's mark is evidence that this cargo is destined for Nero's very own palace, the lavish Domus Aria, the Golden House. This means the ingots belong to Nero himself. And the Beauferrer is sailing for Portus. So she likely sinks before Nero's death in 68 AD. But there's one final question. Why did the Beauferrer and her imperial cargo fail to make it to Portus? The drained wreck offers some clues. The amphorae are off center. They've shifted towards the port side. Such a heavy cargo would never be loaded like this. So what could cause some 5,000 amphorae to move? Carlos believes that the Beauferrer runs into a storm. A large wave strikes the hull, causing the cargo to shift and the vessel to list to her port side, making her impossible to steer and allowing more waves to come over her decks and slowly fill her hold. And then you are done. It's a matter of time. Maybe 20 minutes, maybe one hour, but you are done. As Rome masters the seas, ships like Beauferrer are the empire's lifeblood, carrying precious metals, slaves, and especially grain to and from Portus and harbors all across the Mediterranean, spreading the power and influence of Rome, including a strategic base in modern-day Israel, what the Romans called Judea. Its capital, Caesarea Maritima, stands at the crossroads of Africa and Asia. To the Romans, it's the gateway to the riches of the east, an important source of grain and exotic spices. Transporting these treasures to Rome requires a harbor. But there are major problems. No natural inlets protect from waves. A sandy coastline offers no solid footing for building, and there's a constant threat of earthquakes. But according to historical records, two decades before the birth of Jesus, Roman engineers defy nature here. They construct a grand offshore harbor, transforming Caesarea into a wealthy trade hub. It's a remarkable feat of engineering. Yet today, it's nowhere to be seen. For decades, investigators like National Geographic Explorer Beverly Goodman have been trying to find evidence. We have a pretty good idea of what the harbor might have looked like, because the historian Flavius Josephus left us a record. The entrance of the harbor had towers and statues. You can kind of picture it being this monumental harbor comparable to something you would see in Rome. But over the centuries, the harbor disappears. Only traces of this great Roman outpost remain, scattered on dry land. As for what's left of the harbor itself, the focus of Beverly's investigation must be offshore. What she finds underwater is promising, but far from clear. There's a lot of uncertainty about which parts of the harbor are natural and which of them are the artificial features. There are shapes that could be natural or man-made. Meticulous investigation reveals they're resting on sand. There's no natural bedrock underneath. It's a sure sign they're all man-made and could be part of the lost harbor. Everything that you look at, you realize it was put there. It was placed there. And so then you start to think about that. You start to really understand the scale of what this place was like. To work out the size and orientation of the ancient harbor, the team must first create a comprehensive sonar map of the seafloor. So this kind of survey is getting our baseline maps, our basic information, that from that, we can go and find targets. Combining years of diving surveys with these latest scans, it's possible to drain the waters from the eastern Mediterranean and expose what's left of the ancient harbor of Caesarea Maritima for the first time in almost 2,000 years. As the water recedes, it lays bare a strangely shaped structure on the seafloor. This long, jagged mass of rock, resembling a natural reef, stretches into the empty basin. Opposite, another wider mass reaches out, almost a third of a mile. These are the remains of the breakwaters of a massive port that spanned over 40 acres, the harbor of Caesarea Maritima. So how did the Romans build something so monumental on nothing more than sand? Over 2,000 years ago in Judea, Romans perform an engineering miracle at a place called Caesarea Maritima. They construct the largest artificial harbor in the ancient world. Revealed for the first time in centuries, the foundations of the huge harbor walls had to be built on shifting sand. It seems an impossible task. Beverly Goodman has come to the site of the ancient harbor to take samples from its underwater remains. The team inserts a pipe deep into the seafloor to draw up traces from the past. So we managed to get a core in very deep. Next step is to open it, see what we have inside, see what surprises wait for us. Oh, good. All right, we got quite a few changes we need to log here and take a look at. Wow, this is kind of surprising. I didn't think it was going to have quite so much variation. On the upper part of the core, we have this natural sediment. We really have this period where the site is nearly abandoned for many, many years. Then as we go down the core and we start to get periods where there's actually people around, we start to see more pottery. We start to see rubble. We start to see changes that relate to the fact that people were there and they were influencing the environment they were building. A sediment layer from the time of the harbor reveals a clue. The rubble contains an unusual mineral, a particular type of volcanic ash called pozzolana. It's not natural to this region. The source is over 1,000 miles to the west, the slopes of Mount Vesuvius in Italy. Why bring pozzolana all this way? The reason still lies on the seafloor of Caesarea Maritima, traces of a revolutionary Roman invention, a new kind of concrete. We can actually see those elements of the concrete and know that this is the fingerprint of the presence of the Romans. Historical records reveal that Roman engineers ferry tons of pozzolana to Caesarea. To imagine that they are shipping across the Mediterranean 2,000 years ago, essentially barges that have volcanic ash coming from Italy all the way across the Mediterranean to the Eastern Mediterranean is really something phenomenal. The Romans used concrete to build on land throughout their empire. But then they realized that by adding the pozzolana ash to their concrete mix, they can use it underwater too. They're bringing this volcanic ash in. They're mixing it with the stone rubble and the lime to create concrete. But it only hardens when you pour water on it. So if you take it into the sea, once it hits the water, it hardens. It's known as hydraulic concrete, and it's a huge milestone in the history of construction. For years, how the Romans used this modern building material to create this harbor remains a mystery. But finds on the seabed provide a clue. So one of the findings in Caesarea is preserved wood, wood from 2,000 years ago that was used to create the framework for them to pour the concrete to create these large structures of the harbor. 2,000 years ago, the Romans worked with concrete, just like we do today. They build wooden structures known as caissons that hold liquid concrete in place and then drop them into the sea. Flooded with seawater, the mixture solidifies, creating solid concrete blocks, man-made bedrock on which to build the first artificial harbor in the world. We now know how Caesarea Maritima was constructed, but there's one mystery left. Contemporary accounts suggest the harbor disappears barely a century after its construction. Among the drained ruins, there's a clue to what happened. All the elements of the harbor still remain, but they lie shattered on the seafloor. So what might have led to the collapse of the harbor? In the core samples, layers of sediment from after the construction of the harbor help build a picture of events. When we find these layers and when we see, it's not like the deposits that are above or below it. So we can see that it's, in fact, an isolated incident. These layers suggest that something cataclysmic churned up the sediment. There is a reference that talks about a possible tsunami in the year 115 AD. Maybe that's the event, maybe not. It does coincide nicely with the finds that we have and the ages that we see. It seems likely that this great artificial harbor is reduced to a fraction of its former glory just as Rome tightens its grip on the Mediterranean world. But Caesarea's part in the history of the Roman Empire is not over. The Romans apply the power of their wondrous concrete everywhere, establishing ports and harbors across the Mediterranean wherever they need. This is the first and last time the Mediterranean was under the control of one power. It wasn't a space where wars were fought. It was a place where trade took place. And that's why the Romans have this kind of relationship with the sea. It's our sea, Mare Nostrum. A thousand years will pass before other nations, Portugal and Spain, come close to matching what the Romans achieve, domination of the known world through an empire of the seas.