Sofia is the capital and largest city of Bulgaria, with a population of more than 1,350,000 people. It is located in western Bulgaria, at the foot of the Vitosha mountain, and is the administrative, cultural, economic, and educational centre of the country. One of the oldest cities in Europe, the history of Serdica-Sredets-Sofia can be traced back some 7000 years ago - prehistoric settlements were excavated in the centre of the present city - near the royal palace, as well as in outer districts such as Slatina and Obelia. The well preserved town walls (especially their substructures) from antiquity date back before the 7th century BC, when Thracians established their city next to the most important and highly respected mineral spring, still functioning today. Sofia has had several names in the different periods of its existence, and remnants of the city's millenary history can still be seen today alongside modern landmarks.
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 mountains on all sides. The valley is the largest one in the country with territory of 1,186 square kilometres and average altitude of 550 metres. Three mountain passes lead to the city, which have been key roads since antiquity, connecting the Adriatic Sea and Central Europe with the Black and Aegean Seas.
A number of low rivers cross the city, including the Vladaiska and the Perlovska. The Iskar River in its upper course flows near eastern Sofia. The city is known for its numerous mineral and thermal springs. Artificial and dam lakes were built in the last century.
As to the historic past, Sofia was originally a Thracian settlement called Serdica, possibly named after the Thracian tribe Serdi. Around 500 BC another tribe settled in the region, the Odrysi, known as an ethnos with their own kingdom. For a short period during the 4th century BC, the city was ruled by Philip of Macedon and his son Alexander the Great.
Serdica expanded, as turrets, protective walls, public baths, administrative and cult buildings, a civic basilica, an amphitheatre - the City Council (Boulé), a large Forum, a big Circus (Theatre), etc. were built. When Emperor Diocletian divided the province of Dacia into Dacia Ripensis (at the banks of the Danube) and Dacia Mediterranea, Serdica became the capital of Dacia Mediterranea. The city subsequently expanded for a century and a half, it became a significant political and economical centre, moreso - it became one of the first roman cities where Christianity was recognized as an official religion (Еmperor Galerius). So it was only very natural that Constantine the Great called Serdica (Sardica) "My Rome". Serdica was of moderate size, but magnificent as an urban concept of planning and architecture, with abundant amusements and an active social life. It flourished during the reign of Byzantine Emperor Justinian I, when it was surrounded with great fortress walls whose remnants can still be seen today. The city was destroyed by the Huns in 447 but was rebuilt by Justinian and for a while called Triaditsa. For more than four centuries Sofia was a capital of the Ottoman province of Rumelia. In the 16th century Sofia's appearance became more Oriental with many mosques, fountains and hamams (bathhouses). During that time the town had a population of around 7,000 which rose to 55,000 by the mid 17th century.
Sofia was taken by Russian forces on 4 January 1878, during the Russo-Turkish War, 1877-78, and became the capital of the autonomous Principality of Bulgaria in 1879, which became Kingdom of Bulgaria in 1908. It was proposed for capital by Marin Drinov and was accepted as such on 3 April 1879. By the time of its liberation the population of the was 11,649. For a few decades after the liberation the city experienced a large population growth mainly from other regions of the country.
Later on, during World War II, Sofia was bombed by Allied aircraft in late 1943 and early 1944, as well as later occupied by the Soviet Union. As a consequence of the Russian occupation with the approval of the Allied countries USA, Great Britain, France, Bulgaria's government, which allied the country with Germany, was overthrown by a communist revolution. Like Prague, Warsaw, Bucharest etc. Sofia became a capital of the Communist-ruled People's Republic (1944). The country did not lose territory, but lost vital and important connections with Bulgarian population abroad and all over the world. During that time the population of Sofia expanded at high rates, as a great push has been given to the industrial development of the city - many new large factories and manufacturing plants were built in and around the city. That led to the creation of many new neighbourhoods and expansion of the public transport network.
Nowadays, the historic sites together with many new modern facilities form Sofia's most preferred places of interest. The Sts. Cyril and Methodius National Library (which houses the largest national book collection and is Bulgaria's oldest cultural institute), the Sofia State Library, foreign cultural institutes, the nearly nine-acre amusement park adjacent to the Sofia Zoological Garden (founded in 1888) are all important parts of Sofia's cultural life. Sofia currently enjoys a booming film industry as the filming ground of several international film productions. Vitosha Boulevard, also called Vitoshka — ranked as the world's 22nd most expensive commercial street — represents numerous fashion boutiques and luxury goods stores and features exhibitions by world fashion designers. Sofia's geographic location, situated in the foothills of the weekend retreat Vitosha mountain, further adds to the city's specific atmosphere.