in the southeast angle, and a mihrab in the apse. Since one of the head preachers of the madrasah was named Îsâ ("Jesus" in Arabic and Turkish), his name was added to that of the mosque. The edifice burned down in 1633, was restored in 1636 by Grand Vizier Bayram Pasha, who upgraded the building to cami ("mosque") and converted the north church into a tekke (a dervish lodge). In this occasion the columns of the north church were substituted with piers, the two domes were renovated, and the mosaic decoration was removed. After another fire in 1782, the complex was restored again in 1847/48. In this occasion also the columns of the south church were substituted with piers, and the balustrade parapets of the narthex were removed too. The building burned once more in 1918, and was abandoned. During excavations performed in 1929, twenty-two sarcophagi have been found. The complex has been thoroughly restored between the 1950s and 1960s by the Byzantine Institute of America, and since then serves again as a mosque. Architecture and decoration North church The north church has an unusual quincuncial (cross-in-square) plan, and was one of the first shrines in Constantinople to adopt this plan, whose prototype is possibly the Nea Ekklesia ("New Church"), erected in Constantinople in the year 880, of which no remains are extant. During the Ottoman period the four columns have been replaced with two pointed arches which span the whole church. The dimensions of the north church are small: the naos is long and 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 10th century, the bricks sink in a thick bed of mortar. The building is topped by an Ottoman dome pierced by eight windows. 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 (by the central one)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