Several stories compete in regard to the origins of this building. According to one source, the mosque dates to the Arab siege of A.D. 718, after which it was converted by Dominican Friars into a church. According to John Freely, author of the heavily researched Strolling Through Istanbul, the building was constructed by the Dominicans between 1323 and 1337. The building has undergone quite a bit of repair and additions; it is now once again (if one believes the earlier version) a mosque topped by a belfry/minaret, with an interior courtyard and sadirvan (fountain).