Sofia City Province has an area of 1344 km2. Sofia's development as a significant settlement owes much to its central position in the Balkans. It is situated in western Bulgaria, at the northern foot of the Vitosha mountain, in the Sofia Valley that is surrounded by the Balkan mountains to the north. The valley has an average altitude of 550 metres (1,800 ft). Unlike most European capitals, Sofia does not have any large rivers or bridges, but is surrounded by comparatively high mountains on all sides. Three mountain passes lead to the city, which have been key roads since antiquity, Vitosha being the watershed between Black and Aegean Seas. A number of low rivers cross the city, including the Vladayska and the Perlovska. The Iskar River in its upper course flows near eastern Sofia. The city is known for its 49 mineral and thermal springs. Artificial and dam lakes were built in the twentieth century. While the 1818 and 1858 earthquakes were of very high intensity and were destructive, the 2012 Pernik earthquake occurred west of Sofia with a moment magnitude of 5.6 and a much lower Mercalli intensity of VI (Strong). The 2014 Aegean Sea earthquake was also noticed in the city.
Sofia concentrates the majority of Bulgaria's leading performing arts troupes. Theatre is by far the most popular form of performing art, and theatrical venues are among the most visited, second only to cinemas. The oldest such institution is the Ivan Vazov National Theatre, which performs mainly classical plays and is situated in the very centre of the city.
The National Opera and Ballet of Bulgaria is a combined opera and ballet collective, established in 1891. However, it did not begin performances on a regular basis until 1909. Some of Bulgaria's most famous operatic singers, such as Nicolai Ghiaurov and Ghena Dimitrova, have made their first appearances on the stage of the National Opera and Ballet. The National Palace of Culture regularly hold classical concerts. Bulgaria's largest art museums are located in the central areas of the city. Two emblematic galleries in Sofia – the National Art Gallery and the National Gallery for Foreign Art united their collections in a new structure. Seven Ministers of Culture have worked on this project over the years. The project gathered under one roof a host of Bulgarian, European, American, Asian and African works of art. Nearly two thousand works created by artists from Bulgaria and abroad are on display in twenty eight exhibition halls.
Sofia is one of the most visited tourist destinations in Bulgaria alongside coastal and mountain resorts. Among its highlights is the Alexander Nevsky Cathedral, one of the symbols of Bulgaria, constructed in the late 19th century. It occupies an area of 3,170 square metres (34,122 square feet) and can hold 10,000 people.
Sofia holds Bulgaria's largest museum collections, which attract tourists and students for practical studies. The National Historical Museum in Boyana district has a vast collection of more than 650,000 historical items dating from Prehistory to the modern era, although only 10,000 of them are permanently displayed due to the lack of space.Smaller collections of items related mostly to the history of Sofia are in the National Archaeological Museum, a former mosque located between the edifices of the National Bank and the Presidency. Two natural sciences museums — the Natural History Museum and the Earth and Man — display minerals, animal species (alive and taxidermic) and rare materials. The Ethnographic Museum and the National Museum of Military History are other places of interest, holding large collections of Bulgarian folk costumes and armaments, respectively.