Pernik is a town in western Bulgaria with a population of 70,285 as of 2021. Pernik is the most populated town in western Bulgaria after Sofia. It is the main town of Pernik Province and lies on both banks of the Struma River in the Pernik Valley between the Golo Bardo Mountain, Vitosha Mountain, Lyulin and Viskyar mountains.
Pernik is the principal town of Pernik Province – a province in western Bulgaria, which is next to the Serbian border.
Originally the site of a Thracian fortress founded in the 4th century BC, and later a Roman settlement, Pernik became part of the Bulgarian Empire in the early 9th century as an important fortress.
Wikipedia https://en.wikipedia.org/wiki/Pernik
Coordinates 42°36'33.187" N 23°1'51.405" E