Skopje has some remains of Prehistorical architecture which can be seen on the Tumba Madžari Neolithic site. On the other side of the city lie the remains of the ancient Scupi, with ruins of a theatre, thermae and a basilica. The Skopje Aqueduct,  between Scupi and the city centre, is rather mysterious because its date of construction is unknown. It seems to have been built by the Byzantines or the Turks, but it was already out of use in the 16th century. It consists of 50 arches, worked in cloisonné masonry.