Can this medieval shipwreck rewrite ancient history?

It was the sight of a large bronze medieval cauldron lying on the seabed among some moldering old ship’s timbers that first piqued Igor Miholjek’s interest.

Then head of the Department for Underwater Archaeology at the Croatian Conservation Institute, the state agency that looks after the nation’s cultural resources, Miholjek ran a small team that, in 2014, had been diving around some recently identified shipwrecks. This particular vessel had gone down off the coast of Mljet, one of Croatia’s southernmost Adriatic islands, and he wanted to see if there were any clues that might be worth further investigation.

The wreck itself wasn’t exactly a surprising discovery. Mljet lies along one of antiquity’s main east-west sea trade routes, connecting Italian hubs like Ravenna and Venice with Constantinople (now Istanbul) and points east. Over the years, archaeological surveys of the seabed around the picturesque island, with its Roman ruins and the ancient harbor of Polače at its western tip, had yielded more than two dozen old wrecks, ranging from the remains of a Roman ship from the second century B.C. to that of a 16th-century A.D. Venetian merchantman laden with rare Ottoman ceramics. But even in an area relatively littered with historical wrecks, something about the cauldron told Miholjek that this one was different from the others.

The presence of the old cauldron, together with the scatter of amphorae—large, two-handled pots used since antiquity for transporting wine and olive oil—lying around it suggested that the lost vessel was a Byzantine ship, which would be an extremely rare find in the Adriatic Sea. During his decades-long career, Miholjek and his team had found only one other Byzantine wreck, also off Mljet. But that one had dated from the 11th century A.D. Judging by the shapes and styles of the amphorae he saw on the bottom, this latest discovery was much older, possibly from the late seventh or early eighth century, part of an intriguing period historians used to refer to as the Dark Ages, when the fortunes of the Byzantine Empire were at a low point and when some historians believe that the Adriatic was an impoverished backwater, virtually devoid of shipping.

Yet here was a Byzantine cargo ship lying on the seabed, some 130 feet below the surface. The prospect of excavating the submerged relic was “too good an opportunity to pass up,” Miholjek says, recalling his initial excitement.

Today, after a decade of painstaking progress, Miholjek and his team have uncovered something more astonishing than they could have ever imagined: a rich trove of artifacts that has not only opened a valuable window into travel and trade in the Adriatic at a time when written records were nearly blank but also revealed a glittering, golden mystery. Beyond the predictable objects like anchors and cooking implements, the team recovered a collection of exquisite masculine jewelry—gold buckles, pendants, belt strap ends, and a gold signet ring they believe bears the likeness of Emperor Heraclius, who ruled Byzantium from 610 to 641—a collection that appears to have been the property of a wealthy and well-connected person aboard the ship. Who was he? Where was he headed, and for what purpose?

The search to answer such tantalizing questions is beginning to give historians a glimpse into an empire facing tumultuous times. “Whatever was going on here, this was no normal trading venture,” Miholjek says.

Whatever that mission was, the people conducting it never got beyond Mljet before disaster overtook them, perhaps in the form of a local weather phenomenon known as the bora. A katabatic wind that forms in the mountains running along this stretch of coast, the bora can strike with little warning, roaring down the mountainsides like an avalanche of dense, cold air. Within minutes, it can turn a calm sea into a maelstrom of heaving waves and hurricane-force gusts. Judging by the position of the wreck, Miholjek believes the captain was trying to reach the sheltered harbor at Polače when his ship was overwhelmed.

Jump forward to a sunny summer day in the 21st century, and it’s hard to imagine Mljet as the scene of so much tragedy and loss. With its blue waters and unspoiled landscapes, it’s widely considered one of the world’s most beautiful islands. While the fickle bora wind slowly contributed to the collection of shipwrecks throughout the region, the wreckage has been left undisturbed by a quirk of Iron Curtain elitism. For much of the 20th century, Mljet was largely reserved for use by the Yugoslav military, which meant the wrecks here could not be picked over by sport divers—at least not civilian ones. After the breakup of Yugoslavia in the early 1990s, Mljet became a protected archaeological zone. “It’s a paradise for underwater archaeologists,” Miholjek says.

Despite the potential trove of underwater evidence, excavating the Byzantine wreck was not for the faint of heart. The ship’s remains lay scattered over a steep and rocky seabed at a depth that required the archaeologists to move carefully during each extremely limited dive. For safety reasons, divers could spend just over half an hour a day at the site. What’s more, being short on funds, the team could afford to visit the wreck for only a couple of weeks each summer. This meant that the typically exacting process of underwater archaeology—carefully scanning the area with metal detectors, excavating items from the silt, plotting objects on a grid, and building a 3D map of the site—took even longer than normal.

At first, Miholjek might have expected to unearth the workaday world of an early medieval coastal trader hauling olive oil, wine, and fish sauce from port to port up the Dalmatian coast. But during their third season of diving, the team turned up something that flipped that narrative on its head. On a morning descent near one of the deeper parts of the site, landmarked by a couple of anchors poised on the edge of a steep drop-off, underwater archaeologist Pavle Dugonjić noticed a curious shape in the sand. Sweeping away the silt with his hand, he stared, spellbound, through his mask. It was an exquisitely crafted golden buckle, intricately decorated with birds pecking at grapes from a cornucopia. “I’ve found many beautiful artifacts in the course of my career,” Dugonjić says, “but never anything like this.”

After logging the find on his dive slate—an underwater notepad—and recording its position, he lifted it carefully from the sand and kicked his way to the surface to show his startled colleagues. Over the following six summer diving seasons, the team slowly teased more secrets out of the wreck. They have so far recovered a total of four belt sets (ornamental buckles with matching belt strap ends) all in gold, plus a golden buckle encrusted with rubies, emeralds, and pearls, the likes of which, Miholjek says, have never been found anywhere. They also cataloged the golden imperial signet ring and 14 solidi (chunky gold coins) with Constantinople mintmarks.

Shipwrecks are time capsules, snapshots of life precisely as it was on a particular day. And in addition to the glittering assortment of jewelry and coins, the team recovered a mountain of less eye-catching artifacts—millstones, crockery, fishing tackle, even dice and game pieces used for backgammon or checkers—all parts of a puzzle that with time and much research will be used by archaeologists to tease out an untold story from an obscure past.

Of the ship itself, little remains, just a few waterlogged remnants of its keel, ribs, and planking. But there was enough for Miholjek and the team to surmise it was a fairly standard midsize cargo ship of the time—about 60 feet long, with a capacity of around 60 tons. Judging by the dates on the coins, the types of amphorae, and the workmanship on the jewelry, researchers have refined the dating of the wreck to the first half of the eighth century.

Its location, on the southeastern approach to the harbor at Polače, indicates it was probably sailing north, up the Adriatic, when disaster struck. Miholjek thinks the jewelry and gold belonged to someone wealthy and well-connected aboard the ship, which probably started its fateful voyage in Constantinople and may have been heading for Ravenna, some 300 miles away. Another clue to ponder: The number of amphorae found with the wreck—about a hundred—was only a fraction of what archaeologists would normally expect to find on a ship that size, indicating that something other than bulk cargo was funding the expedition.

The dawn of the eighth century was a troubled time in the history of one of the world’s great empires. Constantinople, the Byzantine capital, was dedicated in 330 and endured for over a thousand years until it was overrun by the Ottoman Turks in 1453. Its inhabitants didn’t think of themselves as Byzantines but as Romans, considering the empire a continuation of ancient Rome. During the centuries following the fall of Rome in 476, the fortunes of the Byzantine Empire ebbed and flowed before rising to a brief golden age under Emperor Basil II in the 11th century.

The latter half of the seventh century was one of the gloomier times. The previous hundred years were characterized by plague, famine, and long, destructive wars against the Persians, leaving the Byzantine Empire in no state to resist the astonishingly swift rise of Islam, whose seemingly unstoppable armies had seized vast territories in the Middle East, Asia, and North Africa after the Prophet Muhammad’s death in 632. The fortunes of the Byzantine Empire were still at a low ebb around 700, by which time the empire had been stripped of its richest provinces by the all-conquering Arabs to the south. Its great seaborne trading days—when wine produced in the Byzantine province of Gaza could be purchased in Britain, and the Harbor of Theodosius in Constantinople bustled with ships carrying grain from Egypt—seemed to be over for good.

The Adriatic virtually disappears from the written record between the seventh and eighth centuries, with little mention of travel or trade on its waters in Latin or Greek. “It’s a blank,” says Francesco Borri, a medieval scholar and associate professor of humanities at the Ca’ Foscari University of Venice who suspects that far more was going on in real life than written records imply. “That’s why the discovery of this ship is so exciting.”

One possibility is that the ship was on a diplomatic mission, bearing gifts of these lavishly decorated belt sets for parties along the Adriatic they hoped to keep friendly to the Byzantine cause. “You can see a clear stylistic connection between the Byzantine Empire and the Avar Empire,” says Falko Daim, professor of early medieval archaeology at the University of Vienna and scholar of Byzantine-era belt sets. “One of the sets from the shipwreck is identical to a set found in an Avar grave that I purchased for the Römisch-Germanisches Zentralmuseum in Mainz when I was a director there. The two sets are so similar they had to have been made in the same workshop.”

The sets, some of which were antiques even at the time of the voyage, appear to have been a collection. “Their dates span almost the entirety of the seventh century,” Daim says. “This is very unusual and makes it difficult to interpret historically.” The newest of them, the one with the birds-and-grapes motif, dates roughly to the early eighth century, not long before the time of the ship’s sinking. The styling is also distinctly Byzantine. “The Avar seldom used birds as motifs. And when they did use them, it was generally an eagle,” he says. “But the Byzantines loved birds.” It’s possible, Daim says, that this belt set was the personal property of the ship’s owner.

Such gilded accessories were a common way to curry favor in this part of the world. “Golden belt sets, even the signet ring of Heraclius, are precisely the sorts of gifts a Byzantine emperor would present,” says Peter Sarris, professor of Byzantine studies at Cambridge University. One recipient of such elegance was a prince named Juanšēr, who ruled Caucasian Albania in the mid-seventh century. To secure the prince’s loyalties, Byzantine emperor Constans II gave him a swag of ornate accessories, including a belt buckle set that had once belonged to Constans’s grandfather, Emperor Heraclius.

It “would have been a much prized gift,” Sarris says. “Anything associated with Heraclius was especially highly regarded.” A signet ring from the emperor would be even grander. “It would be like the British government today giving Winston Churchill’s pocket watch to the leader of a country with which they wanted to stay on good terms,” he says.

Complicating the narrative around the older belt sets is the fact that Miholjek and his team also found goldsmithing equipment in the ship’s wreckage: scales, weights, crucibles, and pools of mercury, an element used by smiths to extract gold from alloys. “Were these simply old-fashioned pieces meant to be melted down and turned into newer, more modern styles?” Daim asks. Was someone on board planning to sell these items or traveling as some sort of emissary? “We have to use our imaginations,” he says. It’s this storytelling potential that intrigues the archaeologists far more than the glint of gold. Until Miholjek and his team found the belt sets off Mljet, such objects had been known almost exclusively from grave sites. “We simply do not have much evidence of these things on the move, just their eventual deposition,” says Justin Leidwanger, associate professor of archaeology and classics at Stanford University. Leidwanger is keen to investigate the economic connections that entangled the empire at the time. “To my mind, this is the most important shipwreck of the period,” he says.

Preliminary studies of the amphorae found with the wreck suggest the ship may have traveled far more extensively around the eastern Mediterranean than historians might have assumed. “We’re finding connections with southern Italy and northern Africa,” Leidwanger says. “This raises interesting questions: Were people from Byzantium still trading directly with North Africa even after the Islamic conquest?”

Much of the surviving text from the seventh century was written by clergy. “Between the rise of Islam and the decline of the empire, they tended to take a bleak view of the times,” Leidwanger says. “We are left with all these descriptions of sacked and abandoned cities.” Yet as scholars have found in western Europe after the fall of Rome, there was still culture, as well as commerce. “The Dark Ages weren’t really all that dark,” he says.

More research remains to be done on the artifacts that Miholjek and his team have brought up from the seafloor. But the idea that sometime around 750 a Byzantine cargo ship could have been sailing north on a diplomatic mission, perhaps bearing gifts for an influential ally, is certainly a new historical theory to ponder. And the details surrounding such a voyage—how the trip would have taken months, how the crew probably passed the time doing mundane things like fishing and playing backgammon—all help humanize the stakes and drive home the emissary’s ambition.

The researchers recently shared plans to return to the site this summer to see what else they might uncover. “Finding all these artifacts brings mixed emotions,” archaeologist Dugonjić says. “Feelings of awe and respect for the passengers and crew who obviously ended their journey on the rocky shores of Mljet, and the pleasure of being able to tell their story”—a story that would otherwise have been lost forever.