The Roman Fort of Carpow was situated at the confluence of the rivers Tay and Earn in what is now Scotland. It was a large fortress with an area of thirty acres occupied by two legions at different times, Legio II Augusta and Legio VI Victrix, and thus of solid, permanent construction using stone, brick and tiles. However, its site on the southern side of the Tay estuary is incompatible with its use as a base for Severan offensive operations to the north and, along with other evidence, it is more likely that the fortress was built under Commodus in 185 to support his campaigns.