Hidden for six centuries under silt and sand at a depth of 13 meters (40 feet) in the Sound strait between Denmark and Sweden, the ship represents a milestone in maritime archaeology. Named Svælget 2 after the channel where it rests, this "medieval super ship" has been preserved in remarkable condition, retaining structural features never before seen in archaeological finds. The discovery came during seabed surveys for Copenhagen's new Lynetteholm district, when divers immediately sensed they had uncovered something exceptional.
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A Medieval Super Ship Emerges
Svælget 2 measures approximately 28 meters (92 feet) long, 9 meters (30 feet) wide, and 6 meters (20 feet) high, with an estimated cargo capacity of 300 tons. Built around 1410 AD, the cog dwarfs previous discoveries of its type and represents the pinnacle of medieval maritime engineering. According to excavation leader Otto Uldum:
"The find is a milestone for maritime archaeology. It is the largest cog we know of, and it gives us a unique opportunity to understand both the construction and life on board the biggest trading ships of the Middle Ages."
The ship's exceptional preservation allowed researchers to analyze details rarely found in shipwrecks. Protected by layers of sand, the starboard side remains intact from keel to gunwale - a first for cog discoveries. Most significantly, archaeologists recovered extensive remains of the ship's rigging, providing crucial evidence about how these massive vessels were sailed.
"It is extraordinary to have so many parts of the rigging," Uldum explained in the Viking Ship Museum announcement. "We have never seen this before, and it gives us a real opportunity to say something entirely new about how cogs were equipped for sailing."
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The cog, named Svælget 2, is exceptionally well-preserved, and previously unseen parts of its rigging emerged during the excavation. The photo shows a ‘deadeye’ used to adjust the ship’s rigging. (Viking Ship Museum)
Revolutionary Design Features Confirmed
For the first time, archaeologists have recovered physical evidence of the tall wooden platforms, or "castles," that adorned the bow and stern of medieval cogs. While countless historical illustrations depicted these structures, no archaeological proof existed until now.
"We have plenty of drawings of castles, but they have never been found because usually only the bottom of the ship survives," said Uldum, as reported by Popular Science. "This time we have the archaeological proof."
The stern castle discovery is particularly significant, with researchers uncovering 20 times more material than any previous find. These covered decks provided shelter and protection for crews, a considerable improvement over Viking Age ships with open decks exposed to harsh weather. "It is not comfort in a modern sense, but it is a big step forward compared to Viking Age ships," Uldum noted.
Another groundbreaking discovery was the ship's brick-built galley - the earliest example ever found in Danish waters. Constructed from approximately 200 bricks and 15 tiles, this cooking area enabled crews to prepare hot meals at sea using an open fire. Bronze cooking pots, ceramic bowls, and remains of fish and meat were recovered nearby, along with hundreds of finely cut sticks possibly used for stockfish. According to Artnet News, this feature "speaks of remarkable comfort and organization on board."
A 3D elevation map reveals the preserved remains of Svælget 2. (Viking Ship Museum)
International Trade Networks Revealed
Dendrochronological analysis (the study of tree rings)revealed that Svælget 2 was constructed using timber from two regions: Pomerania (modern-day Poland) and the Netherlands. The planks came from Pomeranian oak, while the structural frames originated in the Netherlands, where the ship was likely built around 1410. This construction pattern demonstrates the sophisticated medieval trade networks spanning Northern Europe.
"It tells us that timber exports went from Pomerania to the Netherlands, and that the ship was built in the Netherlands where the expertise to construct these very large cogs was found," Uldum explained. The vessel represents a society capable of financing, building, and operating enormous ships to meet the medieval demand for long-distance import and export. A ship of this size required established trade structures where merchants understood market demands for their cargo—likely everyday goods such as salt, timber, bricks, and basic foodstuffs.
The cog revolutionized Northern European commerce during the 14th and 15th centuries. Where long-distance trade had previously been limited to luxury goods, these efficient vessels could transport bulk commodities across vast distances with remarkably small crews. "The cog revolutionised trade in Northern Europe," said Uldum. "It made it possible to transport goods on a scale never seen before."
The medieval ship is dated to around 1410 and, with its length of about 28 meters (92 feet), is the largest cog ever discovered. (Viking Ship Museum)
Life Aboard the Medieval Giant
Personal artifacts recovered from the wreck provide intimate glimpses into daily life aboard these massive trading vessels. Archaeologists discovered painted wooden dishes, shoes, combs, and rosary beads—items that reveal how sailors transferred their land-based routines to life at sea. "The sailor brought his comb to keep his hair neat and his rosary to say his prayers," Uldum observed. "We have the remains of the pots his food was cooked in and the bowls he ate from."
Despite the wealth of personal belongings and ship equipment, the actual cargo remains mysteriously absent. The ship's hold was uncovered, meaning barrels of salt or bundles of cloth would have floated away during the sinking. The absence of ballast suggests Svælget 2 was fully loaded with heavy trade goods when it went down. Researchers found no evidence of military use, confirming the vessel's purely commercial purpose.
The discovery doesn't fundamentally change historians' understanding of medieval maritime trade, but it provides tangible proof of the technological capabilities achieved during this era. "We now know, undeniably, that cogs could be this large—that the ship type could be pushed to this extreme," said Uldum. "Svælget 2 gives us a tangible piece of the puzzle and makes it possible to understand how technology and society evolved side by side in an era when shipping was the driving force behind international trade."
The ship's components are now undergoing conservation at the National Museum in Brede, Denmark. A pop-up exhibition and special tours are being offered at the Viking Ship Museum, where visitors can learn more about this remarkable discovery. The excavation was financed by By & Havn – Copenhagen City & Port Development as part of the Lynetteholm construction project.
Top image: Medieval cog shipwreck underwater excavation showing divers at work on Svælget 2 in the Sound strait between Denmark and Sweden. Source: Viking Ship Museum
By Gary Manners
References
Uldum, O. 2025. Archaeologists reveal a medieval super ship: "It's the world's largest cog". Available at: https://www.vikingeskibsmuseet.dk/en/news/archaeologists-reveal-a-medieval-super-ship-its-the-worlds-largest-cog
Tangermann, V. 2025. The largest Viking shipwreck ever found is absolutely massive. Available at: https://www.popsci.com/science/largest-viking-shipwreck/
Taylor, K. 2025. Remains of a 'Medieval Super Ship' Turn Up in the Waters of Denmark. Available at: https://news.artnet.com/art-world/largest-cog-shipwreck-svaelget-2-denmark-2735069
