Constantinople
Constantinople (; ) was the capital city of the Roman/Byzantine Empire (330–1204 and 1261–1453), and also of the brief Crusader state known as the Latin Empire (1204–1261), until finally falling to the Ottoman Empire (1453–1923). It was reinaugurated in 324 from ancient Byzantium as the new capital of the Roman Empire by Emperor Constantine the Great, after whom it was named, and dedicated on 11 May 330. The city was located in what is now the European side and the core of modern Istanbul.
East–West Schism
The bishop of Byzantium was under the authority of the metropolitan of Heraclea when in 330 Roman Emperor Constantine I moved his residence to this town, which, rebuilt on a larger scale, became known as Constantinople. Thereafter, the bishop's connection with the imperial court meant that he was able to free himself from ecclesiastical dependency on Heraclea and in little more than half a century to obtain recognition of next-after-Rome ranking from the First Council of Constantinople (381), held in the new capital. No Western bishop took part in this council, and the Latin Church recognized it as ecumenical only in the mid-6th century. It decreed: "The Bishop of Constantinople, however, shall have the prerogative of honour after the Bishop of Rome; because Constantinople is New Rome", thus raising it above the sees of Alexandria and Antioch. This has been described as sowing the seed for the ecclesiastical rivalry between Constantinople and Rome that was a factor leading to the schism between East and West. The website of the Orthodox Church in America says that the Bishop of Byzantium was elevated to Patriarch already in the time of Constantine.