Qasr Serij lies near an old route running along the southern foot of the Jabal al-Qusayr between Mosul and Nisibis (cf. Wilkinson, 1990: 50–51, Route B; Wilkinson, 1993: 552). As the name suggests, the site comprises the partly standing remains of a church originally dedicated to St Sergius, a popular eastern saint (Fiey, 1961). It has been identified as the stone church said to have been founded between 559–75 by one Mar Ahudemmeh at a spot known as Ain Qenoye or Ain Qena (‘Spring of Reeds’) in the vicinity of Balad (Eski Mosul) (Fiey, 1958). Preliminary descriptions, accompanied by the first known photographs of the ruins, were made by Gerald Reitlinger (1938: 148–49) and Aurel Stein (finally published in 1985: i, 105–107, Pl. 31c) following their respective surveys of medieval and Roman sites in the Jazira during the wet spring of 1938 (see also Lloyd, 1938: 136, No. 15; Ibrahim, 1986: 74, Site 211). In his subsequent study of the still-unexcavated ruins, David Oates (1962; 1968: 106–17, Pl. XIII) drew architectural parallels with fifth century and later churches in North Syria. Recently, in a series of important articles on early church architecture, Okada (1990; 1991; 1992) has drawn attention to the contrast in plan and fittings of these basilica-type churches with Sasanian and Early Islamic churches in southern Mesopotamia, the Iraqi Western Desert and the Gulf.