The origins of Byzantium are shrouded in legend. The traditional legend has it that Byzas from Megara (a city-state near Athens) founded Byzantium in 657 BC when he sailed northeast across the Aegean Sea. Byzas had consulted the Oracle at Delphi to ask where to found his new city. The Oracle told him to find it "opposite the blind". At the time, he did not know what this meant, but when he came upon the Bosporus he understood: on the opposite eastern shore was a Greek city, Chalcedon, whose founders were said to have overlooked the superior location only 3 kilometres (1.9 mi) away. Byzas founded his city there on the European coast and named it Byzantium after himself. It was mainly a trading city due to its location at the Black Sea's only entrance. Byzantium later conquered Chalcedon, across the Bosporus on the Asiatic side.
After siding with Pescennius Niger against the victorious Septimius Severus, the city was besieged by Roman forces and suffered extensive damage in 196 AD. Byzantium was rebuilt by Septimius Severus, now emperor, and quickly regained its previous prosperity. It was bound to Perinthos during the period of Septimius Severus. The location of Byzantium attracted Roman Emperor Constantine I who, in 330 AD, refounded it as an imperial residence inspired by Rome itself. After his death the city was called Constantinople.
This combination of imperialism and location would affect Constantinople's role as the nexus between the continents of Europe and Asia. It was a commercial, cultural, and diplomatic centre. With its strategic position, Constantinople controlled the route between Asia and Europe, as well as the passage from the Mediterranean Sea to the Black Sea. On May 29, 1453, the city fell to the Ottoman Turks, and again became the capital of a powerful state, the Ottoman Empire. The Turks called the city "Istanbul" (although it was not officially renamed until 1930); the name derives from "eis-tin-polin" (Greek: "to-the-city"). To this day it remains the largest and most populous city in Turkey (the successor to the Ottoman Empire), although Ankara is now the national capital.