Was Byzantium a Christian region

Yes, then it was called Constantinople and now it is Istanbul.___________________________________________________________________________________________

Byzantium [Βυζάντιον] was a small city which was established by the citizens of the ancient city of Megara at 667 BCE. Its name derives from the name of their King Byzas. Later in history the city became the capital of the East Roman Empire [Nova Roma] 330 AD/ CE under Constantine I the Great and after his death was named after him Constantinople. For 11 centuries was the capital of the Byzantine Empire. At 1453 AD/ CE the city was conquered by the Ottoman Turks and became the capital city of the Ottoman Empire until its fall at 1923 AD/ CE. In 1930 the city was renamed as Istanbul and although Ankara is the capital city of Turkey Istanbul is recognised as the most important city of Turkey by many.In the course of history Byzantium changed religions according to the ruling authority from the ancient greek religion to christian religion [330 AD/CE] to Islamic today [1453 AD/CE]. Although Turkey is an Islamic country and christians are a minority it hosts the Ecumenical Patriarch of the Eastern Orthodox Church - The Patriarch of Constantinople.