The Metropolis of Nicaea (Greek: Μητρόπολις Νικαίας), was an ecclesiastical province (since the mid-4th century a metropolitan bishopric) of the Patriarchate of Constantinople in the city of Nicaea in the province of Bithynia (now Iznik in Turkey). A prestigious see due to its proximity to the Byzantine capital, Constantinople, and the location of two Ecumenical Councils in 325 and 787, the metropolitan see of Nicaea remained important until its conquest by the Ottoman Turks in 1331. The Christian element in the diocese diminished rapidly after that, with the flight of the Greek population and the Islamization of the remainder. As a result, the seat of the diocese was moved to Cius. The metropolis remained active until the population exchange between Greece and Turkey in the early 1920s. I