The capital of the country and the largest city in Bulgaria is Sofia, a city located in the western part of the country, at the foot of the Vitosha massif.

An excerpt from the article 34 facts about Bulgaria

The city lies on the Bojana River, which is a left tributary of the Iskar River (the right tributary of the Danube). Sofia is a separate urban region and is also the administrative center of the Sofia Oblast. In 2016, the city had a population of over 1 million 290 thousand people.