Prehistoric art in Scotland Firth. The Romans eventually withdrew to a line in what is now northern England, building the fortification known as Hadrian's Wall from coast to coast. Around 141 CE they undertook a reoccupation of southern Scotland, moving up to construct a new "limes" between the Firth of Forth and the Firth of Clyde, where they built the fortification known as the Antonine Wall. The wall was overrun and abandoned soon after 160 and the Romans withdrew back to the line of Hadrian's Wall, until Roman authority collapsed in the early fifth century. The Antonine Wall and its associated forts left a
City Wall and Moat wooden towers. 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. In the late 19th century, the city wall and its moat lost their strategic significance. By the early 1900s, the wall had