Rila Monastery, a Unesco World Heritage Site, is worth a visit, not only for the harmonious beauty of its buildings (often inaccessible), but also for the artistic treasures it houses. Visitors can access the Church of the Nativity, with its breathtakingly sumptuous ornamentation. The history museum also houses some undeniable masterpieces of Bulgarian religious art. The chapel, Hrelja's Tower and monastery library are also worth seeing.