Stara Zagora (Bulgarian: Стара Загора, pronounced [ˈstarɐ ˈzaɡorɐ]) is a city in Bulgaria, a nationally important economic center. Located in Southern Bulgaria, it is the administrative capital of the homonymous Stara Zagora Province. According to Operative Program Regional Development of Bulgaria, the agglomeration of Stara Zagora is the fifth largest in Bulgaria and has a population of 213,444 inhabitants. Stara Zagora is known as the city of straight streets, linden trees, and poets. The favourable geographic and climatic conditions of the territory around Stara Zagora contributed to the establishment of several prehistoric settlements in the remote past. More than 100 prehistoric mounds from the 6th to 3rd millennium BC were found in the vicinity of Stara Zagora. One of them, the Bereketska mound, is the largest in Bulgaria, containing traces of people that lived there from the New Stone Age (6th millennium BC) to the Middle Ages (12th century). A prehistoric settlement can be found within the city itself. Stara Zagora is the administrative centre of its municipality and the Stara Zagora Province. It is about 231 kilometres (144 mi) from Sofia, near the Bedechka river in the historic region of Thrace.