At the southern edge of Sweden, not far from the picturesque town of Ronneby, lies a tiny island called Stora Ekon. Sprinkled with pine trees, sheep and a few deserted holiday cottages, the low-lying island is one of hundreds that shelter the coast from the storms of the Baltic Sea. For centuries, the spot was a popular anchorage point, but the waters are now mostly quiet; the most prominent visitors, apart from the occasional pleasure boat, are migrating swans. 

Area map
Guibert Gates

For a few weeks in May, however, a new island intruded on this peaceful scene: A square wood raft topped with two converted shipping containers just a few hundred feet from Stora Ekon’s shoreward coast. The floating platform was busy with divers and archaeologists, here to explore what lies beneath the waves: the wreck of a ship called Gribshunden, a spectacular “floating castle” that served as the royal flagship of King Hans of Denmark more than 500 years ago. Historical sources record how the ship sank in the summer of 1495, along with a large contingent of soldiers and Danish noblemen, although not the king himself, who was ashore at the time. 

Shipwrecks from this period are exceedingly rare. Unless a ship is buried quickly by sediment, the wood is eaten away over the centuries by shipworm, actually a type of saltwater clam. But these organisms don’t survive in the fresher waters of the Baltic, and archaeologists believe that much of Hans’ vessel and its contents are preserved. That promises them an unprecedented look at the life of a medieval king who was said to travel with an abundance of royal possessions, not only food and clothing but weapons, tools, textiles, documents and precious treasures. More than that, the relic provides a unique opportunity to examine a state-of-the-art warship from a little-understood period, when a revolution in shipbuilding and naval warfare was reshaping geopolitics and transforming civilization. What Gribshunden represents, researchers think, is nothing less than the end of the Middle Ages and the birth of the modern world.

At the edge of the raft, Brendan Foley, an archaeologist from Lund University in Sweden, and his chief safety officer, Phil Short, are getting ready to dive. Despite the springtime sun, a cold wind blows. Because the water temperature is below 50 degrees, the divers are wearing drysuits and heated underwear that will allow them to work for two hours or more. After extensive planning and a long pandemic delay, Foley is visibly eager to enter the water. “I’ve been waiting for this moment for two years,” he says. He steps off the deck with a splash and makes an OK sign before disappearing from view. 

King Hans of Denmark
King Hans of Denmark Tarker / Bridgeman Images

The story of Gribshunden is preserved in several “Chronicles,” narrative histories written in northern Europe in the 16th century, and in an eyewitness account by a young nobleman who survived the disaster. The accounts describe how King Hans, who reigned over Denmark and Norway from 1481 to 1513, sailed east from Copenhagen in the summer of 1495 toward Kalmar, Sweden, to attend a political summit. Europe was then emerging from the Middle Ages into the Renaissance. Dukes and kings ruled from giant castles, and every nobleman’s wardrobe included a suit of armor. In Italy, Leonardo da Vinci was starting work on The Last Supper. In Poland, Nicolaus Copernicus was beginning his studies in astronomy.

Across the Baltic Sea, Denmark, Norway and Sweden had been ruled together under an agreement called the Kalmar Union for close to 100 years, but Sweden had broken away, and rebels there, led by a nobleman named Sten Sture, sought independence. Hans was on a mission to quell the dissent and revive the union by becoming king of Sweden, too. According to the accounts, Hans took a suitably regal fleet of 18 ships, led by Gribshunden, which carried his courtiers, noblemen, soldiers, even a royal astronomer. 

But many of them never arrived: Hans’ flagship sank while anchored just north of Stora Ekon. A 16th-century account of Hans’ life, only recently translated from Latin, suggests the ship’s store of gunpowder accidentally ignited, causing a fire that consumed the ship so quickly that many on board perished in the smoke and flames. Others threw themselves into the water and drowned. The source adds that the fire occurred while the king was attending a meeting of supporters, probably on Stora Ekon. Other sources record the treasures that sank with the ship: “clothes, precious things, seals and letters,” and “silver, gold, charters and the king’s best stores.” 

Local divers came across the wreck’s protruding timbers in the summer of 1971, unaware of its historical significance, and they collected the curious lead balls they found nearby as souvenirs. One of the divers finally alerted local archaeologists to the wreck in 2001, after he found strange, hollowed-out logs resting on the seafloor: carriages, researchers realized, that once held cannons. This was no fishing boat or trading vessel, it turned out. It was a centuries-old warship of a type never before seen. 

In northern Europe, boats were long built by riveting together overlapping planks to make a waterproof shell. Viking longships, with their rounded hulls and single, square sails, used this “clinker” construction method. In southern Europe, by contrast, there was a tradition of “carvel” construction, in which hull planks were placed edge to edge. In the 15th century, carvel planking spread north, becoming the design of choice for kings and noblemen throughout Europe. Carvel-built hulls gained their strength from the internal ribs, or skeleton, which also made it easier to build larger ships that could carry extensive cargo, crew and stores. And crucially, in contrast to clinker vessels, they could accommodate gun ports, which meant that heavy guns could be carried deep inside the hull without toppling a ship. “Scandinavian ships were beautiful and elegant and sailed to Iceland and Greenland,” says Filipe Castro, a nautical archaeologist previously based at Texas A&M University. “But when the opportunity to put guns on them came along,” he continued, they proved inadequate.

By the end of the 15th century, shipwrights in Portugal and Spain were combining northern and southern features to build heavily armed, uniquely large vessels that could cross oceans, spend months or even years at sea, and extend awesome military force. These were the “space shuttles,” as Castro calls them, that carried the explorers of the Age of Discovery: Christopher Columbus on his Spanish-sponsored voyage across the Atlantic in 1492; the Portuguese admiral Vasco da Gama, who sailed 12,000 miles around Africa, arriving in India in May 1498; and Ferdinand Magellan, who embarked on the first circumnavigation of the Earth (completed after his death in 1522). They allowed for “a new globalization through colonization and exploitation,” writes Johan Rönnby, a maritime archaeologist at Sweden’s Sodertorn University. “The looting and transportation of gold, spices, sugar and many other goods across the oceans changed the world forever.” Or, as Foley, puts it: “This was the enabling technology for European domination of the planet.” 

a page from an illuminated copy of a medieval narrative known as Froissart’s Chronicles, illustrated in the 1470s, shows the French Navy at sea. Scholars believe that the warship at center closely resembles Gribshunden.
Gribshunden belonged to the first generation of ships to cross oceans and reach distant lands. The large vessels combined rounded, Nordic-style hulls constructed from ribs and planks in ways pioneered by shipwrights in Spain and Portugal. Above, a page from an illuminated copy of a medieval narrative known as Froissart’s Chronicles, illustrated in the 1470s, shows the French Navy at sea. Scholars believe that the warship at center closely resembles Gribshunden. They make particular note of the gun ports, heraldic banners and shields, and the sculpted figurehead. Left, King Hans of Denmark. British Library / Granger, NYC

But no example of these carvel-built “ships of discovery,” Iberian or otherwise, had ever been found intact, a deficit Castro describes as “one of the big holes in our puzzle.” Specialists have had to infer their design from artist interpretations and a few surviving miniature models, and had only the murkiest understanding of how this revolutionary technology spread through Europe. 

That was about to change. In 2013, Niklas Eriksson, an archaeologist and expert in medieval ships at Stockholm University, inspected the wreck off Stora Ekon. The Swedish historian Ingvar Sjöblom had speculated that the wreck was Gribshunden, based on its age and location, but others, including Eriksson, were skeptical. “I thought it can’t be,” he told me. 

But when he saw the wreck himself he was amazed. The hull was larger than reported—nearly 100 feet long—and there were remains of elevated, built-up areas, known as castles, that protruded out at the bow and stern. Moreover, the construction of the hull suggested the ship could only have belonged to the king. A chronicle of the life of Sten Sture, the Swedish rebel, described the long-lost Gribshunden as a rare “kraffweel,” or carvel, and what Eriksson realized during his dive was that the wreck’s hull planks were laid edge to edge. It really was Hans’ royal ship: one of these pioneering vessels had been hiding in the shallow green waters of Sweden all along. 

When Foley first learned about the wreck, he didn’t believe it either. “I thought if it was important, I’d have heard of it already,” he says, sitting in a makeshift office on the dive platform. On the table is an espresso machine he proudly tells me is the same model featured in The Life Aquatic, Wes Anderson’s irreverent homage to the marine explorer Jacques Cousteau.

Foley is a 52-year-old American with a genial manner and a sense for the dramatic. He trained with the oceanographer Bob Ballard, who discovered the Titanic, and he now specializes in exploring underwater vessels of all types, from planes to submarines. He spent several years excavating a first-century B.C. cargo ship near the Greek island of Antikythera that sank with clay vessels, coins, bronze and marble artworks, and, most famously, a sophisticated mechanical device described as the world’s oldest “computer.” Before he came to Stora Ekon, he had been working for the U.S. military, recovering the remains of servicemen from crashed World War II bombers, one off Croatia and another off Sweden.

His journey to Stora Ekon began in 2017, after he joined his wife, Maria Hansson, a Swedish geneticist based in Lund, from Massachusetts, where Foley had worked at MIT and the Woods Hole Oceanographic Institution. When his new colleagues told him about Gribshunden, he assumed they were hyping a local attraction. Then he attended a meeting with Rönnby, Eriksson and colleagues from the National Museum of Denmark in Copenhagen. “They were telling me about the wreck, and I said, Are you kidding me? The only known example of a ship of discovery, the first example of a purpose-built warship—and it’s sitting in just nine meters of water?!” 

Brendan Foley lifting a box
One facet of the Gribshunden project is a comprehensive study of the wooden barrels in the ship's hold. Dendrochronology reveals not only when the trees were cut, but where they grew. Chemical and biological analysis may determine the contents of the barrels. Here, Brendan Foley lifts a box containing wooden barrel components from the water, while archaeologists Paola Derudas and Marie Jonsson stand by. Klas Malmberg

The site had already been mapped, and a few artifacts salvaged, including a giant, fearsome figurehead, carved to resemble a monster swallowing a screaming man. But, partly because of the cost, only limited excavations had been carried out. Foley formed a consortium of Swedish and Danish institutions and secured funding from the Crafoord Foundation, founded by the entrepreneur behind Tetra Pak, a multinational food packaging conglomerate, to explore further. In 2019, Foley conducted an initial excavation with Rönnby, who had led several previous studies of the wreck. Foley has been trying to return ever since. Days before work was set to begin this spring, two members of the research team informed Foley they couldn’t join (one was recovering from Covid, another had his visa rejected). Then Foley found himself in the hospital facing emergency surgery for gallstones. “I almost called it off,” he says.

Instead, with his doctors’ approval and orders to follow a strict diet, he went ahead. The international group of experts he’s assembled has set up a white scaffold on the seabed to define their excavation trench, choosing a site near the stern—an educated guess about where the royal quarters were located. 

Down on the seabed, Foley and the other divers work in pairs—an archaeologist with a dive specialist. They sift through layers of debris, including firewood and smashed barrels. Farther down, everything is encased in a fine black sediment that “jiggles like jello,” Foley says. To remove it, the archaeologists use trowels or paintbrushes and suck up the resulting debris clouds into the hose of a dredge pump—like a giant vacuum cleaner—to keep the water clear. (Later, they sift through the “dredge pile” to make sure they don’t overlook any items of interest.) They also record every stage of the excavations by taking hundreds of photographs and videos that Paola Derudas, a data specialist from Lund University, builds into 3-D virtual maps of the site. At the ship’s stern, ghostly timbers, covered in marine growth, jut upward out of the silt. Elsewhere, the hull has split open and fallen outward, resulting in a jumble of planks that lie scattered in the green light. “It’s a beautiful mess!” says Mikael Björk, an archaeologist from Sweden’s Blekinge Museum. But once you get to know it, “you get a sense of the ship,” he says. “You can feel the story.” 

3D model of the wreck site
Three-dimensional models of the wreck site, composed of 4,000 individual images, were updated each day to track the excavation’s progress. Paola Derudas, Lund University; Images by Brett Seymour

Artifacts recovered in 2019 hinted at the ship’s luxurious cargo: a concreted lump of silver coins, high-quality chain mail, and a fine alder wood tankard incised with a crown symbol. Now, over the course of three weeks, the divers unearth a panoply of additional items. A louse comb, plainly made from wood, attests to everyday life on a cramped ship that probably housed more than 150 souls. But there are signs of riches as well: more silver coins, a delicately stitched red-and-black suede slipper, and stores of exotic spices, including peppercorns, cloves and an enormous stash of saffron that when first uncovered “dyed the water red,” says archaeologist Marie Jonsson, of Denmark’s Viking Ship Museum, who found it.

Even more unexpected is the discovery of several panels of elaborately decorated birch bark. One is embossed with a detailed peacock design; another shows an enigmatic beast that resembles a unicorn and still holds traces of gold paint. Eriksson suggests that the king, who received audiences on board during his travels, would have made sure his chambers were sumptuously decorated with textiles and tapestries. “I think it was very fancy on board this ship.”

Riveted brass rings from the neckline or sleeves of a hauberk, or mail armor shirt, worn by a soldier. Hundreds of the rings have been found. Magdalena Caris
Among the many weapons recovered from Gribshunden is the broken handle of a bollock dagger, so named for its suggestively phallic appearance and by the fact that it was often carried in front and low from a soldier’s belt. Åke Nilsson / Blekinge Museum
Birch bark panels, embossed with floral and animal motifs, may have adorned a quiver—several crossbows have also been recovered from the site. Åke Nilsson / Blekinge Museum
A double-sided comb, probably carved from boxwood. Sailors would have used the coarse teeth to groom their hair; the fine teeth removed fleas and lice. Åke Nilsson / Blekinge Museum
These peppercorns were among the exotic spices imported from India or even farther east; others include saffron, clove and safflower. Åke Nilsson / Blekinge Museum
An alderwood tankard bears a symbol resembling a crown. Chemical analysis showed the cup was stained red—color of the Danish royal household. Brett Seymour

These extravagances were not only for Hans’ personal comfort. “The king amassed on his flagship everything and everyone to impress the Swedish noblemen waiting in Kalmar,” Foley says. Of course, Hans didn’t rely on soft power alone. The riches on display were backed up by the threat of violence.

Two hours after Foley and Short enter the water they emerge with a small collection of new artifacts. Foley holds up what looks like a giant wooden fork. “Nice back scratcher!” jokes Björk. The oversized item is soon identified as a linstock, used in naval warfare to hold the burning fuse when lighting a cannon. A carved symbol on the handle—two vertical strokes and a slanted horizontal—may be an owner’s mark. The prongs are charred from use.

Brendan Foley and Phil Short
Brendan Foley, chief archaeologist, and Phil Short, dive specialist, recover an oak gun carriage—the tenth found so far. Others remain in place. Klas Malmberg

It is one of several items that attest to Gribshunden’s military might. The iron cannons themselves have mostly rusted away, but nine wooden gun carriages have previously been recovered, and Foley’s team soon adds a tenth. These range from five to nine feet long and would have held swivel guns in the ship’s bow and stern castles, as well as along both sides of the deck. The archaeologists also discover a 13.5-foot-long gun carriage that is far larger than any other previously found. For the time, says Foley, it was “enormous”—too large to have been positioned across the ship without blocking the deck. He suggests it may be an early example of what’s known from later warships as a “stern chaser,” used to fire off the back.

One historical source suggests that Gribshunden sailed with 68 guns, and based on the finds so far this could be accurate. That means the ship represented a revolution not just in ship design but in naval warfare. Medieval sea battles were essentially land battles carried out on a ship—the aim was to board an enemy vessel and fight hand to hand with swords and spears. But the wide-scale transition to larger, carvel-plank ships, combined with the invention of explosive artillery, enabled purpose-built warships fitted with huge cannons and ports that could support massive guns. That led, during the 16th century, to ships that could destroy enemy vessels and battled almost exclusively from a distance, with a design that persisted with few changes until the 19th century. 

But the early history of these purpose-built warships is “surprisingly poorly understood,” says Kay Smith, an independent expert who previously worked at the Royal Armories at England’s Tower of London. To discover Gribshunden is “absolutely amazing,” she says. The guns on board were essentially wrought-iron tubes, built from hoops and staves like a barrel, which sat in wooden beds and were lit via powder chambers at the rear. Despite the enormous stern chaser, no gun ports have yet been found, and Smith notes that the other guns are still relatively small: for shooting combatants rather than sinking ships. “It’s a key find for our understanding of how ships and armaments were developing.” 

gun carriage recovery
The gun carriages recovered from the ship are the earliest examples of naval artillery ever found, and shed new light on the transition to modern combat. Marie Jonsson

The next day, Foley emerges from his dive with a broad smile. “We found something that has never been recovered before,” he calls from the water. A few minutes later, relaxing on deck with a mug of steaming coffee, he explains that deep in the trench, just above the ship’s hull, he uncovered an intact crossbow, more than three feet long. “Showroom quality,” he gushes. “I mean, it’s still got the bow string! It’s got all the decorations. I’ve never seen anything like it.” He puts down his coffee, runs to the edge of the deck and does a victory somersault into the sea.

Weapons experts are similarly thrilled. Guy Wilson, of the Royal Armories, who specializes in early hand weapons, says that dated examples of crossbows from this period are practically nonexistent. The new find appears to be of a relatively advanced design and will be crucial for understanding the development of this quintessential medieval weapon. In fact, the team seems to have stumbled across what Foley describes as “a small arms locker.” By June, they recover no fewer than four complete crossbows, as well as components from several others, plus numerous wooden arrows, known as quarrels, with their wood, leather or feathered flights intact. The team also recovers the wooden stock from an arquebus, or early handgun, as well as the suggestively carved handle of a “bollock dagger,” popular among sailors and used for penetrating an opponent’s armor. “To have another dated example of European arms technology, 50 years before the Mary Rose”—a warship belonging to Henry VIII that sank in 1545—“is very exciting,” says Wilson. “It’s going to be amazingly important.”

The items will take years to study. Wilson points out that it took three decades to complete the analyses of the artifacts recovered from the Mary Rose. Already, though, Gribshunden is providing a glimpse of warfare on the cusp of transition, as hand weapons gave way to powerful artillery and, with that, the capacity to wage war from a distance—a distinctly modern power that still shapes conflict today.

The sun sparkles on the water, and two swans make a synchronized landing on the waves outside the floating office. Foley opens up his laptop and focuses on detailed scans and graphs on his screen. It’s here, as much as on the seabed, that the science gets done, he says. In addition to the excavation, Foley is collaborating with material scientists, chemists, geologists and others to analyze artifacts he recovers as well as those previously salvaged from Gribshunden but never studied. CT scans of silver coins found in 2019 reveal they are Danish. Intriguingly, however, little else is. Scans of chain mail uncovered the name of a 15th-century metalworker from Nuremberg, Germany. Isotope analysis shows the lead cannonballs are also German. Meanwhile, dendrochronology, the analysis of tree rings in wood, shows that storage barrels came from ports across the Baltic, from Sweden to Poland to Latvia. Combined with the exotic spices, the findings show that Hans was “a surprisingly cosmopolitan king,” Foley says. Eriksson agrees. “Gribshunden shows just how global medieval Denmark was during this time,” he says. 

Perhaps most surprising is an analysis, published this summer, of oak timbers from the ship itself, showing that it wasn’t Danish either. The trees were felled in the early 1480s, matching the ship’s presumed date of construction. (The ship was first mentioned in a 1486 letter written by Hans while on board.) But its timbers evidently came from hundreds of miles away, along the river Meuse, and it was likely built where the Meuse meets the sea, in what’s now the Netherlands. The implication is that after Hans came to power he wanted a pioneering, world-beating ship, but he didn’t yet have the resources or know-how to build it himself, so he ordered it from specialists abroad. 

A circa 1495 rendering of Gribshunden.
A rendering of Gribshunden circa 1495. Mats Vänehem

Despite its likely origin in a Dutch shipyard, however, a new analysis has revealed surprising details about the ship’s construction. The broader switch to carvel planking happened in different ways in different regions: Dutch shipbuilders, for example, built the hull first and added the internal ribs later, whereas the Iberians constructed the frames first using specialized gauges and molds. The Iberian method—which was itself borrowed from the Italians, who learned it from the Byzantines—required sophisticated mathematical knowledge, but it was ultimately more efficient, giving ship designers greater control over the shape of the finished vessel; it was no accident that these vessels came to dominate global exploration. 

This year, Rönnby and his colleague Jon Adams, a maritime archaeologist at England’s University of Southampton, examined detailed measurements of the hull’s timbers, and the early results suggest the hull was built according to the frame-first Iberian style—something no scholar expected. Castro, who was not involved in the study, says that seeing this ship design so far north at this time would be “exciting and important,” evidence of a “porous” world “where knowledge was traveling a lot faster and residing in more places than we previously thought.” And it means that “shipbuilding in the Baltic was not that far behind, if it was behind at all.” Like the famous explorers and conquerors of the Iberian peninsula, northern Europe was “ready to build ships that could carry guns and sail into the horizon.” 

This shipbuilding effort underscores Hans’ ambitions as king, says Per Seesko, a researcher at the Danish National Archives. Records show that, before it sank, Hans had sent Gribshunden as far as England, to negotiate fishing rights, and possibly farther afield. When he sailed to Kalmar with Gribshunden, it was the equivalent, Foley says, of bringing “a nuclear-powered aircraft carrier”: a projection of political and military might and, Hans hoped, proof that he was Sweden’s rightful king. For audiences used to smaller, traditional longboats, the sight of it must have been jaw-dropping. And when it sank, it was more than an embarrassment, or an economic blow, or a tragedy for the lives lost on board—“it was a military setback.”

Afterward, Hans continued on to Kalmar without his flagship, but his rival, the Swedish leader Sture, was delayed, and Hans, perhaps nervous about the comparison between Sture’s military resources and his own now-depleted fleet, didn’t wait for him. He returned home without the Swedish crown. Two years later, he conquered Stockholm by force, but he soon lost the country again. He spent the rest of his reign fighting to get it back. In 1523, Sweden won outright independence from Hans’ son, Christian II. 

Scholars such as Seesko and Foley like to play a parlor game about what might have happened if Gribshunden hadn’t sunk. “It was a turning point in history,” says Foley. “You might have had this Danish Nordic state emerge as a great power,” a united Scandinavia to rival England under Henry VIII. There’s no telling how the map of Europe would have come to look. Even today the European Union might be balanced by a separate northern force. 

Gribshunden's figurehead
Gribshunden's figurehead, recovered in 2015, protruded from the stem, and was carved to resemble a sea monster swallowing a screaming man. Ingemar Lundgren / Blekinge Museum

There are also hints that Hans had bigger ambitions than control of the Baltic. A 16th-century letter reveals that Hans’ father, Christian I, dispatched his own northern voyage of discovery, financed by the Portuguese, that may have followed a route past Greenland into the North Atlantic that we know the Vikings traveled centuries earlier when they temporarily settled in North America. Some historians read the evidence as showing that, 20 years before Columbus arrived in the Americas, Christian’s ship reached “cod country”: Newfoundland. 

Seesko says that Hans “would have been aware” of his father’s explorations, and Foley believes that Hans may well have had ambitions to cross the Atlantic. “We have this dynamic, forward-looking, ambitious king,” he says. If Hans had conquered Sweden in 1495, perhaps he might have pushed even farther. “Hans was trying to do something new,” Foley says. “He was trying to empire-build.” Rather than being built like a ship of discovery, then, meant to project power among his rivals in the region, perhaps Hans intended for Gribshunden to be a ship of discovery itself, with a mission to reach across the northern Atlantic toward an unknown world. 

It’s another day on the temporary island. The cold wind has gone and the water is as calm as a mirror. It’s time for another dive, and Foley’s head is full of what else might be hidden in the sediment. King Hans’ writing desk? The earliest known gun port? Human bones, from crew or noblemen trapped on board as Gribshunden sank? The joy of this wreck is that “we never know what’s going to come up,” Foley once told me. “Every day there is something new.” He adjusts his mask and steps into the water. Bubbles rise as he descends half a millennium back in time. 

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