The Haghia Sophia (Aya Sofya) is a church dating back to 1228-1263. It houses some very fine frescoes. It is a major sight of the city.

This is probably John the Baptist, Christ himself is dropping out of sight (that must mean the bottom part of the fresco was lost, I am not a barbarian). It's a new edit of a slide I scanned again and edited in 2018.