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
Architecture of Scotland Trimontium, and a continuous fortification between the Firth of Forth and the Firth of Clyde known as the Antonine Wall, built in the second century AD. Beyond Roman influence, there is evidence of wheelhouses and underground souterrains. After the departure of the Romans there were a series of nucleated hill forts, often utilising major geographical features, as at Dunadd and Dunbarton. Castles arrived in Scotland with the introduction of feudalism in the twelfth century. Initially these were wooden motte-and-bailey constructions, but many were replaced by stone castles with a high curtain wall. In the late Middle Ages new castles were