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.
Ecumenical Patriarch of Constantinople
The (arch)bishopric of Constantinople has had a continuous history since the founding of the city in 330 AD by Constantine the Great. After Constantine the Great had enlarged Byzantium to make it into a second capital city in 330, it was thought appropriate that its bishop, once a suffragan of the Exarch of Thrace and Macedonia, the Metropolitan of Heraclea, should be elevated to an archbishopric. For many decades the heads of the church of Rome opposed this ambition, not because anyone thought of disputing their first place, but because they defended the 'Petrine principle' by which all Patriarchates were derived from Saint Peter and were unwilling to violate the old order of the hierarchy for political reasons.
In 381, the First Council of Constantinople declared that "The Bishop of Constantinople shall have the primacy of honour after the Bishop of Rome, because it is New Rome" (canon iii). The prestige of the office continued to grow not only because of the obvious patronage of the Byzantine Emperor but because of its overwhelming geographical importance.