Dutch maritime archaeologists have uncovered the remains of the world’s largest medieval cog, a 28‑metre timber vessel hidden for six centuries beneath the sands of the Sound. The ship, known as Svælget 2, surfaced during seabed investigations for Copenhagen’s new Lynetteholm district, shedding new light on the movement of goods across Northern Europe during the medieval period.
“The find is a milestone for maritime archaeology,” according to Otto Uldum, maritime archaeologist and leader of the excavation. “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.”
For the first time, researchers have uncovered physical evidence of the high timber “castles” long depicted in medieval illustrations. These bow and stern platforms, drawn in 14th‑ and 15th‑century illustrations, had never been found in an archaeological context because most wrecks preserve only their lower hulls.
According to Uldum, that gap has now been closed. “We have plenty of drawings of castles, but they have never been found because usually only the bottom of the ship survives. This time we have the archaeological proof.”
His team uncovered extensive remains of a timber‑built stern castle, a covered deck where the crew could shelter from weather and rough seas. The scale of the material is unprecedented, offering researchers a rare opportunity to understand how these structures were built and used.
“We now have 20 times as much material to work with,” Uldum said. “It is not comfort in a modern sense, but it is a big step forward compared to Viking Age ships, which had only open decks in all kinds of weather.”
Measuring 28 metres long, 9 metres wide and 6 metres high, Svælget 2 is the largest cog ever discovered, with an estimated cargo capacity of 300 tonnes. Built in 1410, the ship operated during a time when Northern Europe’s maritime economy was booming and when builders were pushing the limits in boatbuilding.
Dendrochronological analysis shows the vessel was built in the Netherlands using timber sourced from two regions: Pomeranian oak for the planking and Dutch timber for the frames. The combination reveals a sophisticated supply chain in which large quantities of timber were transported across the Baltic and North Seas.
“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 confirmed. He added that the construction pattern suggests the heavy planking was imported while the frames were cut locally at the building site.
The ship’s preservation is remarkable. Buried at a depth of 13 metres, the starboard side remained fully protected from currents and marine organisms, allowing archaeologists to uncover rigging components rarely preserved in medieval wrecks.
“It is extraordinary to have so many parts of the rigging,” Uldum said. “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.”
Another surprise came with the discovery of a brick‑built galley, the earliest example ever found in Danish waters. Around 200 bricks and 15 tiles formed a cooking hearth where sailors could prepare hot meals, a significant improvement over the cold, dried food typical of earlier seafaring.
In the same area, archaeologists found bronze cooking pots, ceramic bowls, painted wooden dishes, shoes, combs, rosary beads and food remains, including fish and meat, offering a vivid portrait of daily life aboard a 15th‑century ship.
“The sailor brought his comb to keep his hair neat and his rosary to say his prayers,” Uldum said. “We have the remains of the pots his food was cooked in and the bowls he ate from.”
Despite the ship’s size, no cargo has been found. The hold was uncovered, meaning barrels of salt, cloth, or timber likely floated away during the sinking.
The absence of ballast suggests the ship was fully loaded when it went down. What is clear, however, is that Svælget 2 was not a warship, and archaeologists found no evidence of conflict or military use. “There is no evidence pointing to war or conflict in this ship,” Uldum said. “None at all.” The vessel instead reflects a society capable of organising large‑scale trade across vast distances.
“Perhaps the find does not change the story we already know about medieval trade,” Uldum said. “But it does allow us to say that it was in ships like Svælget 2 that this trade was created.”
Wood Central understands that the ship’s components are now undergoing conservation at the National Museum in Brede, with its story to be featured in Gåden i dybet (Mystery in the Deep), a new documentary series from Denmark’s national broadcaster.
