A construction crew digging foundations for an office building on Lootsi Street in Tallinn hit wood just 1.5 meters below the surface on March 31, 2022. The timber belonged to a 14th-century merchant vessel, 24.5 meters long, nine meters wide, and four meters tall, sealed under the city since the 1360s. The Estonian Maritime Museum identified it as one of the largest medieval shipwrecks recovered in Europe in the past century.
Moving it took three months of preparation and 13 hours of transport. Engineers cut the hull into four sections just to get it out of the ground. Tree-ring dating later placed the ship’s construction timber at around 1360, the period when Hanseatic merchant fleets dominated trade across the Baltic and North Seas.
A peer-reviewed study published in March 2026 in the Journal of Cultural Heritage has since raised new questions about where the ship was built and how it came to rest beneath a downtown Tallinn street.
The Compass Nobody Expected to Find
The most arresting object recovered from the wreck is a dry compass, reported by Estonian public broadcaster ERR to be the oldest surviving example of its kind in Europe. Dry compasses work through a magnetized needle pivoting freely over a compass rose, without liquid stabilization. This one still functions after more than six centuries underwater.
Priit Lätti, an archaeology researcher at the Estonian Maritime Museum, said the state of the ship’s interior pointed to a sudden sinking rather than a planned abandonment. Tools, weapons, and worn leather shoes lay scattered where they had been left. “I don’t think the inventory was just left on the ship, it was most likely a shipwreck,” Lätti said. “People had to get off the ship in a hurry and everything was left in a mess.”
Researchers also recovered two well-preserved ship rats, which offer direct physical evidence of what life aboard a medieval Baltic trading vessel actually looked like, something rarely captured in the archaeological record.
Tree Rings Point to an Unexpected Origin
The 2026 study, published in the Journal of Cultural Heritageon ScienceDirect, ran tree-ring analysis across multiple plank groups from the hull. Most of the oak matched timber sources in northern Poland, typical for Hanseatic shipbuilding of this era.
One cluster of planks did not fit that pattern. Their rings matched a sequence found in a door still hanging in the Bremen Tower, part of Tallinn’s medieval city walls, wood previously linked to the Tallinn hinterland or western Lithuania. That correlation led researchers to ask whether the ship was built in western Lithuania and completed for its first voyage in Tallinn before it sank near the harbor.
The study stops short of a firm conclusion, but confirms the hull was assembled from timber sourced across more than one region, which was standard practice in large Baltic shipbuilding of the period.
The Ship That Has Baffled Specialists for Three Years
The Lootsi cog designation is official, but the vessel has resisted easy classification since the excavation began. As ERR reported in 2023, Lätti told a national television audience that several structural features simply do not match the accepted definition of a cog.
Standard cogs were sealed with moss. This ship used pitch-covered animal fur alongside it. Certain plank configurations in the hull were, until this find, believed to have appeared in shipbuilding roughly a century later.
“Colleagues from abroad, who have seen more of these kinds of wrecks, have thrown up their hands and said they are not aware of anything similar,” Lätti said. The Estonian Maritime Museum continues to use the cog label in official communications while vessel classification research remains open.
A Second, Older Ship Remains in the Ground
The Estonian Maritime Museum is currently cleaning the hull, tracking moisture levels to prevent the wood from drying or developing mold, and collecting samples for laboratory analysis in Estonia and abroad. Finnish conservators are working on the project alongside museum archaeologists.
Lätti confirmed that an even older wreck sits buried nearby and has not been touched. His reasoning is straightforward: the ground has preserved it for centuries, and better excavation methods may eventually allow a more complete recovery. Any timber that surfaces during future construction in the area will be handled under archaeological monitoring, the same process that brought the Lootsi cog to light in 2022.
The Lootsi cog is scheduled for permanent public display at the Estonian Maritime Museum once conservation work is complete.
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