The White Tower is the most iconic symbol of the city. The tower was constructed by the Ottomans sometime in the early 15th century and once guarded the eastern end of the city's sea walls. In the 19th century, this tower was used as a notorious prison. Nowadays, it is a welcoming museum of art and local history. The museum offers a rapid lesson in the history of the city. Ideally, you'll take in this well-dosed overview before continuing to the more specialised museums and archaeological sites. For best results, grab the free audio guide at the entrance. The last floor of the tower gives you a wonderful view of the city.

Unique in Greece, the Rotunda is a cylindrical building from the early 4th century AD. The mosaics inside are really impressive. The Rotunda is a massive circular structure, built in 306 AD, with a masonry core. Through its long history, it has gone through multiple periods of use and modification as a polytheist temple, a Christian basilica, a Muslim mosque, and a Christian church once again. A minaret is preserved from its use as a mosque, and ancient remains are exposed on its southern side. Some Greek publications claim it is the oldest Christian church in the world. These days, the Rotunda is primarily an archaeological site, where you can see some remaining Christian mosaics and feel the weight of history.

This gorgeous Russian Orthodox church is located in central Sofia. It was built by Russia after the liberation of Bulgaria. The grave of Saint Archbishop Seraphim is located under the main floor - believers still visit for pilgrimages, leaving notes with wishes and prayers.