The largest collection of antique shipwrecks ever found in Norway has been discovered under mud at the building site for a new highway tunnel in Oslo, Norway. Jostein Gundersen, project’s lead archeologist said at least nine wooden boats, the largest being 17 metes long, were found well preserved nearly 400 years after they sank at Bjoervika, an Oslo inlet near the new national opera house.

The wrecks were remarkably well preserved because they had been covered in mud and fresh water, where river waters run into the sea. It was believed that the wrecks have sunk sometime after a massive fire swept the wooden buildings of old Oslo in 1624. After that disaster, Danish-Norwegian King Kristian IV ordered the city center moved before reconstruction started.

The discovered boats were moored at the old port which became a remote area after the city was moved. It was assumed that the boats may have been 30 or 40 years old when they sank. The wreckage will be moved as quickly as possible, so construction of the undersea tunnel can continue.