Constantinople (Greek: Κωνσταντινούπολις, Κωνσταντινούπολη - Konstantinoúpolis, Konstantinoúpoli; Latin: Constantinopolis; Ottoman Turkish: قسطنطینیه, Kostantiniyye; and modern Turkish: İstanbul) was the capital city of the Eastern Roman or Byzantine Empire, the Latin and the Ottoman Empire. It was founded in AD 330, at ancient Byzantium as the new capital of the Roman Empire by Constantine the Great, after whom it was named. In the 1100s, the city was the largest and wealthiest European city of the Middle Ages, its only other European rival in the period being Cordova, Spain (900-1100 AD). Eventually, the empire of Christian Eastern Orthdoxy in the east was reduced to just the capital and its environs, falling to the Muslims in the historic battle of 1453.

The city itself remained and prospered as the Muslim capital in the Ottoman period; however, scholars normally reserve the name "Constantinopole" for the city in Christian period 330-1453, preferring "Istanbul" for the city's name in later centuries. However, many Western writers have continued to refer to the city by its older name "Constantinople" into modern times. And the name "Constantinople" is still used by the 300 million members of the Eastern Orthodox Church in the title of their most important figurehead, the Orthodox patriarch based in the city, referred to as "His Most Divine All-Holiness the Archbishop of Constantinople New Rome and Ecumenical Patriarch."

Constantinople was famed for its massive defenses. Although besieged on numerous occasions by various peoples, it was taken only in 1204 by the army of the Fourth Crusade, in 1261 by Michael VIII Palaiologos, and - finally - in 1453 by the Ottoman Sultan Mehmed II. A first wall was erected by Constantine I, and the city was surrounded by a double wall lying about 2 km (1.2 miles) to the west of the first wall, begun during the 5th century by Theodosius II. The city was built on seven hills as well as on the Golden Horn and the Sea of Marmara, and thus presented an impregnable fortress enclosing magnificent palaces, domes and towers.

It was also famed for architectural masterpieces such as the church of Hagia Sophia, the sacred palace of the emperors, the hippodrome, and the Golden Gate, lining the arcaded avenues and squares. Constantinople contained numerous artistic and literary treasures before it was sacked in 1204 and 1453. It was virtually depopulated when it fell to the Ottoman Turks, but the city recovered rapidly, becoming once again by the mid 1600s the world's largest city as the Ottoman capital Istanbul.

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