This is what remains (after a total restoration in 1833) of the St. Helen’s Church (Ayaelena Kilesesi), which is supposed to be founded by Empress Helena, mother of Constantine the Great (she who found the true cross and many more objects when she went to Jerusalem. Read “The innocents abroad” by Mark Twain for a hilarious description of all that). It was used as a mosque from 1920 on, was closed when I visited, but as promised in the Lonely Planet Guide some remains of Christian furniture could be distinguished through a window.