Attackers had to construct bridges from their wooden towers in order to reach the top of the wall, thus exposing themselves to the defenders of the city. Archaeologists have not been able to provide a precise date for the construction of the city wall and its moat, although historical chronicles suggest the 9th century. Both wall and moat were built atop the Phoenician cemetery, and cut across the ruins of the Phoenico-Persian, Hellenistic and Roman residences.