The Roman amphitheatre called Arena is built in the dominant location above the harbour. It was erected in the 1st and the 2nd centuries, with an elliptic ground-plan (133 x 105 m), and the walls 32.5 m high. The Amphitheatre could contain 20,000 spectators. It is the sixth greatest amphitheatre in the world. The location of the permanent theme exhibition on Istrian olive and wine growing in antiquity in the basement of the amphitheatre has demanded the reconstruction of the reinforced concrete ceiling and the interior design. According to the project demands, the dilapidated ceiling slate, positioned alongside the central part of the arena, has been removed, and a new one, leaning against prestressed reinforced concrete girders and pillars, has been constructed. The stone walls in the subterranean vaults have been constructed by using the traditional methods and materials – hand-manufactured stone and mortar, according to the old prescriptions.