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). South church The south church is a square room surmounted by a dome, and surrounded by two deambulatoria, an esonarthex and a parekklesion (added later). The north deambulatorium is the south parekklesion of the north church. This multiplication of spaces around the central part of the church, typical of late Palaiologian architecture, was motivated by the need for more space for tombs, monuments erected to benefactors of the church, etc. The central room is divided from the aisles by a triple arcade. During the mass the believers were confined in the deambulatoria, which were shallow and dark, and could barely see what happened in the central part of the church. The masonry is composed of alternated courses of bricks and stone, typical of 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 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 middle and late Byzantine Architecture in Istanbul. See also History of