Sofia's motto is "It grows, but does not age", and the city has been proving it for a long time. The Thracians settled here for the hot springs, the Romans built Serdica on top of them, and Constantine the Great is supposed to have called it "my Rome". Under the Ottomans it was for three centuries the seat of the governor of Rumelia, a town of mosques and markets, and after Bulgaria was freed in 1878 the new state picked it as capital and rebuilt it in a hurry, with a royal palace, yellow cobbles and grand boulevards. Then came forty-five years of communism, and the concrete and statues that came with it.
All of that is still on show, often within a few meters. In the middle of town, a 4th-century church, an Ottoman mosque, an Orthodox church and a synagogue stand within sight of each other, and you walk over Roman streets on your way to the metro. Sofia isn't pretty in the way Prague is, and it doesn't pretend to be. It's lively, green, cheap by European standards, and it has a 2,290 m mountain, Vitosha, at the end of the tram line.
Day one is the old center and its layers, day two the boulevard of the Liberation, Alexander Nevsky and the icons, day three Boyana and the slopes of Vitosha, day four a trip to Rila Monastery, and day five socialist Sofia and the parks. Most museums close on Mondays, and the synagogue on Saturdays, so starting on a Tuesday works best. For the rest of the country, see Bulgaria.