Şeyh Süleyman Mosque
The Sheikh Suleiman Mosque (Turkish Şeyh Süleyman Mescidi) originally was a Byzantine structure near the Pantocrator Monastery in Constantinople.
Neither its identity nor its function is known. Even though it often argued that it is a Palaiologan structure, the masonry indicates that it originated from an earlier period. It has been suggested that it was a mausoleum from the Early Byzantine era. Later it might have been used as a library of the Pantocrator Monastery.
It consists of a central hexagonal superstructure with pendentives rising on a square substructure. There are four semicircular niches on the corners of the square and is surmounted by a shallow dome. Each of the walls that constitute the octagon have pointed arches on the outside, pointing to a later Ottoman renovation. The southern niche was walled up and transformed into a mihrab when it was converted into a mosque.
The building was converted into a mosque by Sheikh Suleiman in the reign of Mehmed II. It was damaged by a fire in 1756, and later restored. It has recently been renovated and is currently closed to the public.
From Byzantine Topographic Studies by Paspates (1877)
Plan by Gurlitt
Bildlexikon zur Topographie Istanbuls: Byzantion, Konstantinupolis, Istanbul by Wolfgang Müller-Wiener
Converted Byzantine Churches in Istanbul: Their Transformation Into Mosques and Masjids by S. Kirimtayif