The medieval ship lay more than a half-mile down at the bottom of the Black Sea, its masts, timbers and planking undisturbed in the darkness for seven or eight centuries. Lack of oxygen in the icy depths had ruled out the usual riot of creatures that feast on sunken wood.

This fall, a team of explorers lowered a robot on a long tether, lit up the wreck with bright lights and took thousands of high-resolution photos. A computer then merged the images into a detailed portrait.

Archaeologists date the discovery to the 13th or 14th century, opening a new window on forerunners of the 15th- and 16th-century sailing vessels that discovered the New World, including those of Columbus. This medieval ship probably served the Venetian empire, which had Black Sea outposts.