Rila Monastery is the oldest Orthodox church in the region The Monastery of Saint Ivan of Rila, better known as the Rila Monastery (Bulgarian: Рилски манастир, Rilski manastir) is the largest and most famous Eastern Orthodox monastery in Bulgaria. It is situated in the southwestern Rila Mountains, 117 km south of the capital Sofia in the deep valley of the Rilska River at an elevation of 1,147 m above sea level, inside of Rila Monastery Nature Park.