The wreck of a ship thought to have taken part in a failed Mongol invasion of Japan has been found off the Japanese coast.
A team of researchers uncovered a 12-metre (36ft) section of keel buried in deep sand off Nagasaki prefecture.
They said it was the first time such a large piece of hull had been recovered from the Mongol invasion fleets.
The 13th Century attacks on Japan were a rare setback for the Mongols at the height of their powers.
Experts expressed surprise that the wreck was so well preserved after so many centuries on the seabed.
The researchers from the Okinawa-based University of the Ryukyus used ultrasonic equipment to detect the remains of the ship.
The wood on the hull was painted whitish grey and held together by nails. Bricks, weapons and other instruments were found on board.
The discovery is expected to shed light on the shipbuilding skills of the time and give clues about the nature of the Mongol defeat.
The Japanese have always attributed their victory to storms that wrecked the Mongol fleets during both attempted invasions in 1274 and 1281.
They concluded that Japan was protected from invasion by a divine wind, or Kamikaze, which was invoked in World War II to inspire pilots to launch suicide attacks on allied ships.
As Central Asian nomads, the Mongols had little experience of the sea and used subjugated Chinese and Koreans to build their fleets.
The structure of the ship is said to resemble Chinese ships of the era.
The Mongols that did manage to land are reputed to have had some success against the Japanese, who struggled to match their skilled use of mounted archers.
But on both occasions, the Mongols and the Chinese and Korean troops under their command, headed back out to sea to try to ride out approaching typhoons - and that proved to be their downfall.
BBC News. 2011. "Ship from failed Mongol invasion found off Japan". BBC News. Posted: October 25, 2011. Available online: http://www.bbc.co.uk/news/world-asia-pacific-15452071