Scotland during the Roman Empire soon after 160. The destruction of some of the southern brochs may date to the Antonine advance, the hypothesis being that whether or not they had previously been symbols of Roman patronage they had now outlived their usefulness from a Roman point of view. The Roman frontier became Hadrian's Wall again, although Roman incursions into Scotland continued. Initially outpost forts were occupied in the south-west and Trimontium remained in use but they too were abandoned after the mid-180s. Roman troops, however, penetrated far into the north of modern Scotland several more times. Indeed, there is a greater density of Roman
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