One of the most emblematic monuments of the ancient city of Tarraco. It was built in the first century B.C. From the Roman period it still retains one of its side towers. It has a rectangular base and part is still covered by a barrel arch. The underground vaulted chamber is linked to a passageway. During the Middle Ages the Kings of Aragón redesigned it for use as a Royal Palace. It is currently home to Tarragona's History Museum.