St. George's Cathedral, Istanbul
The Patriarchal Cathedral Church of St. George (Greek: Πατριαρχικός Ναός του Αγίου Γεωργίου; Turkish: Aya Yorgi Kilisesi) is the principal Eastern Orthodox cathedral located in Istanbul, Turkey, formerly Constantinople.
Source: Wikipedia — St. George's Cathedral, Istanbul (CC BY-SA 4.0)