The secrets of the world's oldest sunken city, Pavlopetri off southern Laconia in Peloponnese, Greece, are lost to history, but hi-tech underwater archaeology answers questions that books cannot; experts explore sunken ruins and reveal new discoveries about one of the first great empires. 

Surrounded by a mysterious trench, only one Egyptian pyramid, the Pyramid of Lahun, was ever constructed to look like it floats on water. Using pioneering drone-scanning technology, experts decode the ancient secrets of the pharaoh Senusret II that are locked inside its hidden tunnels.