Ostros Monastery ( Prechista Krajinska Monastery ) is a Serbian medieval monastery located in Skadar Krajina , on the southwestern shore of Skadar Lake , near the villages of Mali and Veliki Ostros , 22 kilometers southeast of Virpazar , near the border with Albania . It is believed that the Gospel of Mary , written in Glagolitic script , is one of the oldest Old Slavic manuscripts from the 11th century, written in this monastery.