Church of St. Mary, Osor (Croatia, island on the Adriatic coast)
The diocese developed in antique urban environment, according to historical sources, in the 6th ct. Archaeological finds in present-day cemetery around St. Mary's chapel (it was built above older antique layer), have evidenced a complex of original early-Christian cathedral from the same century.
Archaeological excavations below the church and on the whole cemetery show that there was also a prehistoric place for worship situated on the same area. In the period from the 5th till the 6th ct. from the time of organized Christian community the whole area below today's cemetery was occupied by the cathedral, baptistery, bishop's palace and other ecclesiastical buildings.
Church of St. Mary has one nave, it was a part of former early-Christian double basilica with a baptistery on the northern side and with preserved remains of earlier sanctuaries. A remnant of antique floor mosaic and fragments of intertwining ornaments are visible in the church, and in the sanctuary itself there is a remnant of bishop's throne, considerably remodelled by the beginning of the 20th ct.