Christianity in Turkey
Constantinople became established in the ecclesiastical hierarchy at the Council of Constantinople in 381. Second only to Rome, the legendary origins of the Patriarchate of Constantinople go back to St. Andrew, Metrophanes and Alexander of Constantinople. Constantinople's primacy over the Patriarchates of Alexandria and Antioch was reaffirmed at the Council of Chalcedon in 481, after which the papacy in Rome supported Constantinople in its dispute with Alexandria over monophysitism. Later, when Rome sought to assert its primacy over Byzantium, the Eastern Orthodox church developed the doctrine of pentarchy as a response.
Europe
The empire continued to expand under emperors such as Antoninus Pius and Marcus Aurelius, who spent time on the Empire's northern border fighting Germanic, Pictish and Scottish tribes. The Empire began to decline in the 3rd century, particularly in the west. Christianity was legalised by Constantine I in 313 AD after three centuries of imperial persecution. Constantine also permanently moved the capital of the empire from Rome to the city of Byzantium, which was renamed Constantinople in his honour (modern-day Istanbul) in 330 AD. Christianity became the sole official religion of the empire in 380 AD, and in 391-392 AD, the emperor Theodosius outlawed pagan religions. This is sometimes considered to mark the end of antiquity; alternatively antiquity is considered to end with the fall of the Western Roman Empire in 476 AD; the closure of the pagan Platonic Academy of Athens in 529 AD; or the rise of Islam in the early 7th century AD.