In 324 the Roman emperor Constantine the Great selected the ancient city of Byzantium as the site of his new capital, which he later named Constantinople. Like Rome, Constantinople was built on seven hills and at one time was surrounded by walls. The walls erected by Emperor Theodosius II in 413 are largely in ruins.
Istanbul is famous as one of the most often besieged cities in the world. Before the Turkish conquest its assailants included the Arabs (673-78, 717-18), the Bulgarians (813, 913), and the armies of the Fourth Crusade, which twice succeeded in taking the city (1203, 1204).
After Constantinople fell to the Turks in 1453, the city became the capital of the Ottoman, or Turkish, Empire; it was the capital of present-day Turkey until 1923, when the newly founded Turkish Republic declared Ankara (then Angora) the capital. The name was officially changed from Constantinople to Istanbul in 1930.
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