Plovdiv is the second largest city in Bulgaria, the 5th oldest in the world and the oldest in Europe. Its history dates back to 4,000 years BC. In the beginning, the ancient settlement was situated on the natural elevation between Nebet, Taksim and Dzhambaz hills (the Three Hills). In ancient times Thracians inhabited the Three Hills and built a fortified settlement – the largest city in Thrace. In the 4th century BC Plovdiv was conquered by Phillip of Macedonia. He gave the city one of its many names – Phillipopolis, and had it surrounded by thick fortified walls. The town hosts the Roman theatre, which was successfully restored and is presently used for performances.