Church of Saint Mary of the Mongols
Fener, Turkey · built 1281
Saint Mary of the Mongols (full name in Greek: (pr. Theotókos Panagiótissa, lit. "All-Holy Theotokos") or (pr. Panaghía Muchliótissa); Turkish name: Kanlı Kilise (meaning: Bloody Church), is an Eastern Orthodox church in Istanbul. It is the only surviving Byzantine church of Constantinople that has always remained a functioning house of worship of the Greek Orthodox Church. It and Hagia Irene are the only two Byzantine churches there never converted into mosques, the latter however being used as an arsenal until the 19th century, and currently operating as a museum and concert hall.
Church data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).