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.
Apostolic see
This Council of Nicaea, being held in 325, of course made no mention of Constantinople, a city which was only officially founded five years later, at which point it became the capital of the Empire. But the First Council of Constantinople (381) decreed in a canon of disputed validity: "The Bishop of Constantinople, however, shall have the prerogative of honour after the Bishop of Rome; because Constantinople is New Rome." A century after the Council of Chalcedon (451) and the ensuing schism between those who accepted it and those who rejected it, Eastern Orthodox Christianity wove these two sources together to develop the theory of the Pentarchy: "[F]ormulated in the legislation of the emperor Justinian I (527–565), especially in his Novella 131, the theory received formal ecclesiastical sanction at the Council in Trullo (692), which ranked the five sees as Rome, Constantinople, Alexandria, Antioch, and Jerusalem." Earlier, the Council of Ephesus decreed in 431 that the Church of Cyprus should be autocephalous, against the claims of Antioch, the capital of the Roman diocese of the East, of which Cyprus was part.