Plovdiv (Bulgarian: Пловдив) is the second-largest city in Bulgaria, and one of the two oldest cities in Europe. It sits on the large plain between the Rhodope Mountains on the south and the Balkan Range (Stara Planina - "Old Mountain") that runs through the centre of Bulgaria to the north. Both ranges are visible on clear days. The Maritsa River flows through the city on its way southeast before forming the Greek/Turkish border to the Aegean Sea.