Roman roads in Britannia the military road from Carlisle to Corbridge, was built under the Emperor Trajan (ruled 98–117 AD) along the line of the future Hadrian's Wall, which was constructed by his successor Hadrian in 122–132 AD. Scotland ("Caledonia"), including England north of Hadrian's Wall, remained mostly outside the boundaries of "Britannia" province, as the Romans never succeeded in subjugating the entire island, despite a serious effort to do so by governor Gnaeus Julius Agricola in 82–84 AD. However, the Romans maintained a system of forts in the lowland region ca. 80–220 AD to control the indigenous population beyond Hadrian's Wall and annexed
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