I visited Bulgaria this August, and I must say that the Rila monastery was one of the most beautiful things I saw there, though I travelled around the country (Sofia, Varna, Plovdiv etc.) and I saw quite a lot if monuments and sights.
I think that the cloister looks fantastic and that it's situated in a gorgeous location, among those fantastic mountains. I really liked those verandahs and balconies, with columns and arches, and the mural paintings were amazing too.