A popular day trip for visitors to Sofia, is the chance to visit the famous Rila Monastery some 120KM to the south of the city. The fantastic building was re-built in 1833 on the site where the original stood, and contains some 1200 frescoes on its walls as well as having a museum that tells the story of the monastery, where Bulgarian culture was kept alive while the country was under Turkish rule from the 1500s.
The monastery was founded in 927AD by the hermit Ivan Rilski, and close by, you can see the cave where he is buried.