The Temple of Hephaestus, also known as the Hephaisteion or earlier as the Theseion, is a well-preserved Greek temple; it remains standing largely as built. It is a Doric peripteral temple, and is located at the north-west side of the Agora of Athens, on top of the Agoraios Kolonos hill. From the 7th century until 1834, it served as the Greek Orthodox church of St. George Akamates.
https://en.wikipedia.org/wiki/Temple_of_Hephaestus