However, the motto of the city is "grows, but does not age".
Remains from another neolithic settlement around the National Art Gallery are traced to the 3rd–4th millennium BC, which has been the traditional centre of the city ever since and is not changed today.
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.
In these documents the city is called Sofia, but at the same time the region and the city's inhabitants are still called Sredecheski (срѣдечьскои, "of Sredets"), which continued until the 20th century.
In the context, certainly the neolithic village in Slatina, dating to the 5th–6th millennium BC, is described.
The 2014 Aegean Sea earthquake was also noticed in the city.
Air pollution is a problem in Sofia due to its location in the Sofia valley, which is surrounded by mountains that reduce the ability of the air to self-clean.
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.
It seems that the first written mention of Serdica was made during his reign and the last mention was in the 19th century in a Bulgarian text (Сардакіи, Sardaki).