Plovdiv is an ancient city built around 7 hills, in southern Bulgaria. The Regional Archaeological Museum chronicles the city’s history, with exhibits including mosaic panels, clay lamps and early coins. The Roman-era Ancient Theatre of Philippopolis, which once seated around 6,000, now hosts opera and concerts. A 3D movie at the Emperor Hadrian–era Ancient Stadium re-creates Plovdiv in the 2nd century A.D.