The Roman Empire did not end at a wall. The walls — Hadrian’s in Britain, the German and Raetian limes, the Fossatum Africae in North Africa — were not barriers in the way that a modern border fence is a barrier. They were administrative lines, surveillance infrastructure, and military positioning systems that defined the edge of Roman tax collection and legal authority rather than the edge of Roman cultural or economic influence. The distinction matters because the popular image of Rome crouching behind its walls against pressing barbarians misrepresents the actual relationship between Rome and the peoples beyond its frontiers — a relationship that was commercial, diplomatic, and culturally interpenetrative as well as occasionally violent.