HISTORY OF BYZANTIUM

The origins of Byzantium are shrouded in legend. The traditional legend has it that Byzas from Megara (a town near Athens), founded Byzantium, when he sailed northeast across the Aegean Sea. Byzas had consulted the Oracle at Delphi to ask where to make 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 realized what it meant: on the Asiatic shore was a Greek city, Chalcedon. It was they who must have been blind because they had not seen that obviously superior land was just a half mile away on the other side of the Bosporus. Byzas founded his city here in this "superior" land and named it Byzantion after himself. It was mainly a trading city due to its strategic location at the Black Sea's only entrance. Byzantion later conquered Chalcedon, across the Bosporus.
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. The location of Byzantium attracted Roman Emperor Constantine I who, in 330 AD, refounded it as Nova Roma. After his death the city was called Constantinople (Greek Κωνσταντινούπολις or Konstantinoupolis) ('city of Constantine'). It remained the capital of the Eastern Roman Empire, which was later called the Byzantine Empire by historians.
This combination of imperialism and location would affect Constantinople's role as the crossing point between two continents: Europe and Asia. It was a commercial, cultural, and diplomatic magnet. With its strategic position, Constantinople could control 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, once again, became the capital of another powerful state, the Ottoman Empire. The Turks called the city Istanbul (though not officially renamed until 1930) and it has remained Turkey's largest (and arguably its most important) city, although Ankara is now the capital.