I'm no Bulgaria expert, just happen to have spent 2 days there. Sofia exceeds my expectation as a "second-tier" city (in the sense that it's not a big metropolis). The area around the Sheraton Sofia Hotel is very nice to walk around, with the Parliament, the Art Museum, the churches and various landmark buildings nearby. This area is marked by the coloured (yellowish?) stones of the road.

I had coffee and cake at "Cafe Bulgari" in this area, very nice indeed. I like Sofia for its quaintness and I think it's worth spending one day relaxing there.