I found this photo on Les Eglises de Constantinople , Jean Ebersolt, Adolphe Thiers. Paris, 1913.
Old St Theodosia Church was built in
Istanbul in the late eleventh or early twelfth century to honour the memory of Virgin Martyr Theodosia. It is said that when the city was captured on May 29, feast of the Saint, the church was decked by roses, hence its Turkish name Gül Camii meaning "Mosque of the Roses". Another theory is that its turkish name comes from the dervish called Gül Baba burried here.
Gül Camii, Istanbul
CC picture from
English Wikipedia entry
Gul Mosque