The area of Knin, Biskupija and its surroundings has a lot of remains of early medieval sacral architecture, considering that in the Early Middle Ages, independent Duchy of Croatia and later Kingdom of Croatia were established in that area. Early medieval churches in the area of Knin, Biskupija and its surroundings were mostly built in the 9th century, probably as a result of the mass christianization of Croats under the influence of the Frankish cultural circle, when already existing churches wer erenovated and a large number of new churches were built. Most of the churches were longitudinally oriented single-nave or three-nave churches. Three-nave churches had three different types of sanctuaries, and single-nave churches had two types of sanctuaries. Three-nave churches like the church of St. Bartholomew at Kapitul in Knin (2.1) and the church of St. Cecilia in Biskupija (2.4) had a three-apsidal sanctuary with a central semicircular apse larger than the semicircularapses on the sides. Other threenave churches, the church of St. Mary in Biskupija (2.5) probably had a three-part sanctuary with a central semicircular apse or a three-part sanctuary inscribed in the eastern flat wall of the church like the church of St. Mary (Crkvina) in Gornji Koljani (2.8). Two types of sanctuaries can be observed in single-nave churches: single-apsed, such as the church on Bukorovića hillock in Biskupija (2.3) and the church of St. John in Uzdolje (2.6), and a triconch or trefoil sanctuary like the church on hillock Lopuška in Biskupija (2.2) and the Church of the Holy Salvation in village Cetina (2.7). The churches were located on hillocks and share many similar characteristics. Today, only the foundations of the churches have been preserved because most of the churches were demolished during the Middle Ages, but some of the churches were demolished in the later period, during the invasion of the Ottomans, and their remains today are very modest because the local population often took stone from the church sites for the construction of other buildings.