There have been several theories as to the origins of this former Byzantine church, but none has emerged as the fitting piece to the puzzle. Some say that it was built by Leo I in A.D. 458 for SS. Peter and Mark. A second theory puts construction in the 9th or 10th century A.D. and suggests that if this were so, it would have been the earliest example of a dome-in-cross church in Constantinople and therefore the precursor for the type of church that spread all over Russia in the 11th century. The building lay abandoned after the Ottoman conquest until it was converted into a mosque several decades later; the dome dates to this period of reconstruction, and many of the early architectural features were lost.