Medieval 'super ship' found wrecked off Denmark is largest vessel of its kind

Archaeologists have discovered a massive medieval shipwreck sitting at the bottom of a strait off Denmark.

The 600-year-old ship was a cog: a round, single square-sailed vessel that was one of the most advanced ship types in the Middle Ages. At around 92 feet (28 meters) long and 30 feet (9 m) wide, the newly-found ship is the largest cog ever discovered, according to researchers at Denmark's Viking Ship Museum.

The researchers discovered the vessel off Copenhagen in Øresund, or "the Sound" in English — the strait between Denmark and Sweden. They described it as a "super ship" that could transport hundreds of tons of cargo at low cost during a period of burgeoning trade in the 14th and 15th centuries.

"The find is a milestone for maritime archaeology," excavation leader Otto Uldum said in a statement. "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 discovery was made accidentally as part of seabed investigations for a new artificial island that Denmark plans to create off Copenhagen. Researchers removed what they described as "centuries of sand and silt" to reveal the outline of the ship, which they named Svælget 2 after the channel in which it was found.

Svælget 2 was well preserved on the seabed, located 43 feet (13 m) below the surface. Sand protected its starboard side, which retained traces of delicate rigging — unheard of in previous cog wrecks. The researchers also identified a brick galley, the first in a medieval ship in Danish waters, which allowed the crew to cook hot meals on an open fire. Artifacts on the ship included cooking materials, such as pots and bowls, and the crew's personal objects, such as hair combs and rosary beads for prayer, according to the statement.

The researchers have yet to find Svælget 2's cargo. Uldum noted that the hold wasn't covered, so cargo barrels would have floated away from the ship as it sank. However, with no signs of military use, Svælget 2 is likely to have been a merchant ship, the researchers said.

Svælget 2 was constructed in 1410, a fact the researchers deduced by tree-ring dating annual growth patterns on the ship's wood. The team also compared the patterns to previously published tree-ring data and determined that the ship's planks were from Poland, while the frame of the ship came from the Netherlands. Furthermore, construction patterns suggested that the planks were imported while the frame was cut at the ship's building site, indicating that the construction relied on a complex timber trade network across Northern Europe, according to the statement.

The giant ship was designed for a perilous journey from the Low Countries (including what is now the Netherlands) to the trading towns of the Baltic. A cog of this size would have allowed for the transportation of bulky everyday goods such as salt, timber, bricks and basic food items over long distances, which the researchers said would have previously only been done for luxury goods.

"The cog revolutionised trade in Northern Europe," Uldum said. "It made it possible to transport goods on a scale never seen before."