A thirteenth century church that became a mosque. The Wikipedia mentions: "The Fatih Mosque is a mosque in Ortahisar district of Trabzon Province, Turkey. It was originally built in Byzantine times as the Panagia Chrysokephalos Church (Greek: Παναγία Χρυσοκέφαλος, "Panagia the Golden-Headed"), serving as both the catholicon for the see of Trebizond, and a church for a monastery until the Ottoman conquest of the city in 1461." From another source I understood the earlier church may have been from 914.
It seems to be called Fatih Mosque, but appears under other names on the web.