Plunging into the waters off Alexandria Tuesday, divers explored the submerged ruins of a palace and temple complex from which Cleopatra ruled, swimming over heaps of limestone blocks hammered into the sea by earthquakes and tsunamis more than 1,600 years ago.

The international team is painstakingly excavating one of the richest underwater archaeological sites in the world and retrieving stunning artifacts from the last dynasty to rule over ancient Egypt before the Roman Empire annexed it in 30 B.C.