Istanbul

Greek legend says Byzas consulted the Oracle at Delphi, who told him to settle 'opposite the land of the blind' — a jibe at earlier settlers who had missed the supreme natural harbour on the European shore. Constantine the Great rebuilt it as Constantinople in 330 CE and declared it the new Rome. After 1,000 years as the heart of the Byzantine Empire, Mehmed II conquered it in 1453 at age 21, armed with the world's largest cannons.