Fenâri Îsâ Mosque (full name in Molla Fenâri Îsâ Câmîsi; Eκκλησία του Λίβος), is a mosque in Istanbul, made of two former Eastern Orthodox churches.
In 908, the Byzantine Admiral Konstantinos Lips, who later perished in 917 fighting against Simeon I's Bulgaria, inaugurated a nunnery in the presence of the Emperor Leo VI the Wise dedicated to the Virgin Theotokos ("Immaculate Mother of God") in a place called "Merdosangaris" (Greek: Μερδοσαγγάρης), in the valley of the Lycus (a river of Constantinople). This establishment, which according to its Typicon hosted a total of 50 women also a Xenon ("hospital") with 15 beds attached, was known also after his name (Monē tou Livos), and became one of the largest of Constantinople. The church was built on the remains of another shrine of the sixth century, and using the tombstones of an ancient Roman cemetery and hosted the relics of Saint Irene. The church was generally known as "North Church".
After the Latin invasion and the restoration of the Byzantine Empire, between 1286 and 1304, Empress Theodora, widow of Emperor Michael VIII Palaiologos, erected another church dedicated to St. John the Baptist (Eκκλησία του Αγίου Ιωάννου Προδρόμου του Λίβος) south of the first church. Several exponents of the imperial dynasty of the Palaiologos were buried there besides Theodora: her son Konstantinos, Empress Eirene of Montferrat and her husband Emperor Andronikos II. This church is generally known as the "South Church".
During the fourteenth century an esonarthex and a parekklesion were added to this church. The habit of burying members of the imperial family in the complex continued also in the fifteenth century with Anna, first wife of Emperor John VIII Palaiologos, in 1417. The church was possibly used as a cemetery also after 1453.
The dimensions of the north church are small: the naos is 13 meters long and 9.5 meters wide, and was sized according to the population living in the monastery at that time. The masonry of the northern church was erected by alternating courses of bricks and small rough stone blocks. In this technique, which is typical of the Byzantine architecture of the tenth century, the bricks sink in a thick bed of mortar. This edifice has three high apses: the central one is polygonal, and is flanked by the other two, which served as pastophoria, prothesis and diakonikon.
The apses are interrupted by triple and single lancet windows. The walls of the central arms of the naos cross have two orders of windows: the lower order has triple lancet windows, the higher semicircular windows. Two long parekklesia, each one ended by a low apse, flanks the presbytery of the naos. The angular and central bays are very slender. At the four edges of the building are four small roof chapels, each surmounted by a cupola.
The remainders of the original decoration of this church are the bases of three of the four columns of the central bay, and many original decorating elements, which survive on the pillars of the windows and on the frame of the dome. The decoration consisted originally in marble panels and coloured tiles: the vaults were decorated with mosaic. Only spurs of it are now visible.
As a whole, the north church presents strong analogies with the Bodrum Mosque (the church of Myrelaion).
The masonry is composed of alternated courses of bricks and stone, typical of the late Byzantine architecture in Constantinople.
The lush decoration of the south and of the main apses (the latter is heptagonal), is made of a triple order of niches, the middle order being alternated with triple windows. The bricks are arranged to form patterns like arches, hooks, Greek frets, sun crosses, swastikas and fans. Between these patterns are white and dark red bands, alternating one course of stone with two to five of bricks. This is the first appearance of this most important decorating aspect of the Palaiologian architecture in Constantinople.
The church has an exonarthex surmounted by a gallery, which was extended to reach also the north church. The parekklesion was erected alongside the southern side of the south church, and was connected with the esonarthex, so that the room surrounds the whole complex on the west and south side. Several marble sarcophagi are placed within it.
As a whole, this complex represents a notable example of the middle and late Byzantine Architecture in Constantinople.