Rila has well developed cultural tourism and contains five of the 100 Tourist Sites of Bulgaria — the Church of Theodore Tyro and Theodore Stratelates in the village of Dobarsko, the Rila Monastery and the Stob Earth Pyramids, the Seven Rila Lakes, the museum of history and the convent in the town of Samokov, and the summit of Musala. Rila Monastery is the most important architectural monument in the mountain range. It is situated at an altitude of 1,147 m and was declared a UNESCO's world heritage site in 1983. The Monastery is considered to be a cultural and spiritual centre of Bulgaria. With its architecture and frescos Rila Monastery represents a masterpiece of the creative genius of the Bulgarian people and has exerted considerable influence on architecture and aesthetics within the Balkan area. Established in the First Bulgarian Empire by the medieval Bulgarian hermit and saint John of Rila during the reign of emperor Peter I of Bulgaria (r. 927-969), the monastery developed into one of the main cradles of Bulgarian culture, literature and spirituality. In the 18th century it became one of the main hubs of the Bulgarian National Revival. The complex covers an area of 8,800 m2 and consists of a five-domed church, a defensive tower and monastic apartments encircling an inner yard. The exterior of the complex resembles a fortress with its high stone walls and little windows. The oldest surviving structure is the 23 m high Hrelyo's Tower, constructed in 1334-1335.