Maritime archaeologists from the Viking Ship Museum in Denmark have announced the discovery of what they describe as the world’s largest cog—a medieval cargo vessel built around 1410 and found in the waters (Øresund) between Denmark and Sweden.
From the first dive, archaeologists realised the outline beneath the sand was not an ordinary shipwreck. As centuries of silt were cleared away, the scale of the vessel became apparent: approximately 28 metres long, 9 metres wide, and 6 metres high, with an estimated cargo capacity of around 300 tons. That size, researchers say, reflects just how large late medieval trading ships could become—and offers a rare chance to examine construction details that are usually lost when only the lower hull survives.
“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,” says Otto Uldum, maritime archaeologist and excavation leader.
The wreck, named Svælget 2 after the channel where it was discovered, was located during seabed investigations connected to Copenhagen’s Lynetteholm development project.
A 15th-century ship built for bulk trade
Photo courtesy Viking Ship Museum
Cogs were among the most important workhorses of late medieval shipping, and Svælget 2 appears to represent the type pushed to an extreme. Otto Uldum argues that a ship of this scale points to a trade system that was already highly organised.
“A ship with such a large cargo capacity is part of a structured system where merchants knew there was a market for the goods they carried,” he notes. “Svælget 2 is a tangible example of how trade developed during the Middle Ages.”
Cogs could be sailed by a relatively small crew, even when heavily loaded, helping merchants move large volumes efficiently. Larger cogs were built to tackle risky routes, including the hazardous voyage around Skagen, travelling from what is now the Netherlands through the Sound and on to Baltic trading towns. Svælget 2, archaeologists suggest, fits squarely into the extensive networks that connected Northern Europe in the 15th century.
“It is clear evidence that everyday goods were traded. Shipbuilders went as big as possible to transport bulky cargo – salt, timber, bricks or basic food items,” Uldum adds.
Timber from Pomerania and the Netherlands
Photo courtesy Viking Ship Museum
One of the most striking results so far comes from dendrochronology (tree-ring dating). Researchers report that Svælget 2 was built around 1410 using timber sourced from two different regions: Pomerania (in modern-day Poland) and the Netherlands. The planks were made from Pomeranian oak, while the ship’s frames (ribs) came from the Netherlands—an arrangement the team interprets as evidence of complex material supply and specialised shipbuilding capacity.
“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 notes.
Unprecedented preservation, with rigging still surviving
Fish bones. Photo courtesy Viking Ship Museum
Svælget 2 is also being presented as an unusually well-preserved cog wreck. Excavated at a depth of 13 metres, it was shielded from many of the destructive forces that normally affect coastal wrecks. Sand is said to have protected the ship’s starboard side “from keel to gunwale,” giving archaeologists access to upper structures and fittings that rarely survive.
Among the most important elements are traces of the ship’s rigging—vital components for controlling the sail and supporting the mast.
“It is extraordinary to have so many parts of the rigging,” Uldum explains. “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.
“The finds show how something as complex as the rigging was solved on the largest cogs. Rigging is absolutely central to a medieval ship, as it makes it possible to control the sail, secure the mast and keep the cargo safe. Without ropes and rigging, the ship would be nothing.”
The first secure archaeological evidence for cog “castles”
Medieval art frequently depicts cogs with high timber-built platforms—“castles”—at the bow and stern. Yet archaeologists have long lacked definitive physical evidence for these structures, largely because wrecks typically preserve only the lower hull. According to the Viking Ship Museum team, Svælget 2 changes that.
“We have plenty of drawings of castles, but they have never been found because usually only the bottom of the ship survives,” Uldum says. “This time we have the archaeological proof.”
Researchers report extensive remains of a timber-built stern castle, described as a covered deck where crew could shelter from the elements—particularly significant on large merchant voyages.
“We now have 20 times as much material to work with. 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,” Uldum adds.
A brick-built galley and traces of meals at sea
Fragment of a turned wooden dish, approximately 25% preserved. Original diameter about 40 cm, height about 3 cm, thickness about 5 mm. The decoration consists of incised contours with applied color: radial triangular lines on the center, a checkerboard pattern (approx. 7×7 mm) on the rim, and a narrow band with intersecting zigzag lines. The paint now appears black-gray with traces of lighter colors. The dish shows no signs of use. Photo courtesy Viking Ship Museum
Another major surprise is the ship’s brick-built galley, described as the earliest example of its kind from Danish waters. Archaeologists report finding around 200 bricks and 15 tiles, along with bronze cooking pots, ceramic bowls, and food remains.
“We have never before seen a brick galley in a medieval ship find from Danish waters. It speaks of remarkable comfort and organisation on board. Now sailors could have hot meals similar to those on land, instead of the dried and cold food that previously dominated life at sea,” says Otto Uldum.
In the same area, the team also found hundreds of finely cut sticks that may have been used for stockfish—one more hint of the ship’s provisioning and daily routines.
Shoes, combs, rosary beads: everyday life on a merchantman
One of two combs that were found in the shipwreck. Both are made of wood and feature fine teeth on one side and larger teeth on the other. Combs were common tools in the Middle Ages and were used both for hair care and for keeping hair free of lice. Photo courtesy Viking Ship Museum
Beyond the ship itself, Svælget 2 has yielded personal and domestic objects that rarely survive in such quantity. The excavation uncovered painted wooden dishes, shoes, combs, and rosary beads, alongside cooking and eating equipment.
“The sailor brought his comb to keep his hair neat and his rosary to say his prayers. We have the remains of the pots his food was cooked in and the bowls he ate from. These personal objects show us that the crew brought everyday items with them. They transferred their life on land to life at sea,” explains Otto Uldum.
What was Svælget 2 carrying?
Bronze cooking pot from Svælget 2. Photo courtesy Viking Ship Museum
Despite the ship’s impressive size, archaeologists say they have found no direct trace of the cargo—only items that can be explained as ship’s gear or crew possessions.
The archaeologists suggest that cargo stored in an uncovered hold—such as barrels of salt, bundles of cloth, or timber—could have floated away during the sinking. The absence of ballast, the team notes, may indicate the ship was loaded heavily with trade goods when it went down. Even without the cargo, researchers stress that the evidence points to a merchant vessel rather than a warship.
“There is no evidence pointing to war or conflict in this ship. None at all,” Uldum stresses.
A ship as “a mirror of society”
Phot3D model of the shipwreck Svælget 2 after excavation. The 3D models were created using photogrammetry, a technique that combines hundreds of high-resolution photographs to generate precise digital reconstructions of the ship’s structure and details. Image courtesy Viking Ship Museum
For the researchers, Svælget 2 is not only a technological landmark but also a reflection of late medieval economic capacity—financing, organising, and supplying a vessel of this size required more than individual ambition.
“It required a society that could finance, build and equip these enormous ships that served the Middle Ages’ need for export and import over great distances,” says Otto Uldum.
“Perhaps the find does not change the story we already know about medieval trade. But it does allow us to say that it was in ships like Svælget 2 that this trade was created. We now know, undeniably, that cogs could be this large – that the ship type could be pushed to this extreme. 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 Brede Works of the National Museum of Denmark.
Maritime archaeologists from the Viking Ship Museum in Denmark have announced the discovery of what they describe as the world’s largest cog—a medieval cargo vessel built around 1410 and found in the waters (Øresund) between Denmark and Sweden.
From the first dive, archaeologists realised the outline beneath the sand was not an ordinary shipwreck. As centuries of silt were cleared away, the scale of the vessel became apparent: approximately 28 metres long, 9 metres wide, and 6 metres high, with an estimated cargo capacity of around 300 tons. That size, researchers say, reflects just how large late medieval trading ships could become—and offers a rare chance to examine construction details that are usually lost when only the lower hull survives.
“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,” says Otto Uldum, maritime archaeologist and excavation leader.
The wreck, named Svælget 2 after the channel where it was discovered, was located during seabed investigations connected to Copenhagen’s Lynetteholm development project.
A 15th-century ship built for bulk trade
Cogs were among the most important workhorses of late medieval shipping, and Svælget 2 appears to represent the type pushed to an extreme. Otto Uldum argues that a ship of this scale points to a trade system that was already highly organised.
“A ship with such a large cargo capacity is part of a structured system where merchants knew there was a market for the goods they carried,” he notes. “Svælget 2 is a tangible example of how trade developed during the Middle Ages.”
Cogs could be sailed by a relatively small crew, even when heavily loaded, helping merchants move large volumes efficiently. Larger cogs were built to tackle risky routes, including the hazardous voyage around Skagen, travelling from what is now the Netherlands through the Sound and on to Baltic trading towns. Svælget 2, archaeologists suggest, fits squarely into the extensive networks that connected Northern Europe in the 15th century.
“It is clear evidence that everyday goods were traded. Shipbuilders went as big as possible to transport bulky cargo – salt, timber, bricks or basic food items,” Uldum adds.
Timber from Pomerania and the Netherlands
One of the most striking results so far comes from dendrochronology (tree-ring dating). Researchers report that Svælget 2 was built around 1410 using timber sourced from two different regions: Pomerania (in modern-day Poland) and the Netherlands. The planks were made from Pomeranian oak, while the ship’s frames (ribs) came from the Netherlands—an arrangement the team interprets as evidence of complex material supply and specialised shipbuilding capacity.
“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 notes.
Unprecedented preservation, with rigging still surviving
Svælget 2 is also being presented as an unusually well-preserved cog wreck. Excavated at a depth of 13 metres, it was shielded from many of the destructive forces that normally affect coastal wrecks. Sand is said to have protected the ship’s starboard side “from keel to gunwale,” giving archaeologists access to upper structures and fittings that rarely survive.
Among the most important elements are traces of the ship’s rigging—vital components for controlling the sail and supporting the mast.
“It is extraordinary to have so many parts of the rigging,” Uldum explains. “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.
“The finds show how something as complex as the rigging was solved on the largest cogs. Rigging is absolutely central to a medieval ship, as it makes it possible to control the sail, secure the mast and keep the cargo safe. Without ropes and rigging, the ship would be nothing.”
The first secure archaeological evidence for cog “castles”
Medieval art frequently depicts cogs with high timber-built platforms—“castles”—at the bow and stern. Yet archaeologists have long lacked definitive physical evidence for these structures, largely because wrecks typically preserve only the lower hull. According to the Viking Ship Museum team, Svælget 2 changes that.
“We have plenty of drawings of castles, but they have never been found because usually only the bottom of the ship survives,” Uldum says. “This time we have the archaeological proof.”
Researchers report extensive remains of a timber-built stern castle, described as a covered deck where crew could shelter from the elements—particularly significant on large merchant voyages.
“We now have 20 times as much material to work with. 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,” Uldum adds.
A brick-built galley and traces of meals at sea
Another major surprise is the ship’s brick-built galley, described as the earliest example of its kind from Danish waters. Archaeologists report finding around 200 bricks and 15 tiles, along with bronze cooking pots, ceramic bowls, and food remains.
“We have never before seen a brick galley in a medieval ship find from Danish waters. It speaks of remarkable comfort and organisation on board. Now sailors could have hot meals similar to those on land, instead of the dried and cold food that previously dominated life at sea,” says Otto Uldum.
In the same area, the team also found hundreds of finely cut sticks that may have been used for stockfish—one more hint of the ship’s provisioning and daily routines.
Shoes, combs, rosary beads: everyday life on a merchantman
Beyond the ship itself, Svælget 2 has yielded personal and domestic objects that rarely survive in such quantity. The excavation uncovered painted wooden dishes, shoes, combs, and rosary beads, alongside cooking and eating equipment.
“The sailor brought his comb to keep his hair neat and his rosary to say his prayers. We have the remains of the pots his food was cooked in and the bowls he ate from. These personal objects show us that the crew brought everyday items with them. They transferred their life on land to life at sea,” explains Otto Uldum.
What was Svælget 2 carrying?
Despite the ship’s impressive size, archaeologists say they have found no direct trace of the cargo—only items that can be explained as ship’s gear or crew possessions.
The archaeologists suggest that cargo stored in an uncovered hold—such as barrels of salt, bundles of cloth, or timber—could have floated away during the sinking. The absence of ballast, the team notes, may indicate the ship was loaded heavily with trade goods when it went down. Even without the cargo, researchers stress that the evidence points to a merchant vessel rather than a warship.
“There is no evidence pointing to war or conflict in this ship. None at all,” Uldum stresses.
A ship as “a mirror of society”
For the researchers, Svælget 2 is not only a technological landmark but also a reflection of late medieval economic capacity—financing, organising, and supplying a vessel of this size required more than individual ambition.
“It required a society that could finance, build and equip these enormous ships that served the Middle Ages’ need for export and import over great distances,” says Otto Uldum.
“Perhaps the find does not change the story we already know about medieval trade. But it does allow us to say that it was in ships like Svælget 2 that this trade was created. We now know, undeniably, that cogs could be this large – that the ship type could be pushed to this extreme. 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 Brede Works of the National Museum of Denmark.
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