n.
formerly Constantinople ancient Byzantium
City and seaport (pop., 1997: 8,260,438), Turkey.
Situated on a peninsula at the entrance to the Black Sea , Turkey's largest city lies on either side of the Bosporus and thus is located in both Europe and Asia. Byzantium was founded as a Greek colony in the 8th century BC. Passing to the Persian Achaemenian dynasty in 512 BC and then to Alexander the Great , it became a free city under the Romans in the 1st century AD. The emperor Constantine I made the city the seat of the Eastern Roman Empire in 330, later naming it Constantinople. It remained the capital of the subsequent Byzantine Empire after the fall of Rome in the late 5th century. In the 6th13th centuries it was frequently besieged by Persians, Arabs, Bulgars, and Russians. It was captured by the Fourth Crusade (1203) and turned over to Latin Christian rule. It was returned to Byzantine rule in 1261. In 1453 it was captured by the Ottoman Empire and made the Ottoman capital. When the Republic of Turkey was founded in 1923, the capital was moved to Ankara , and Constantinople was officially renamed Istanbul in 1930. Many of the city's historic sites are located in the medieval walled city (Stamboul). Among its architectural treasures are the Hagia Sophia , the Mosque of Süleyman, and the Blue Mosque. Its educational institutions include the University of Istanbul (founded 1453), Turkey's oldest university.