Borders of the Roman Empire

The borders of the Roman Empire, which fluctuated throughout the empire's history, were realised as a combination of military roads and linked forts, natural frontiers (most notably the Rhine and Danube rivers) and man-made fortifications which separated the lands of the empire from the countries beyond. == Limes == The word limes is sometimes used by modern scholars to denote the frontier of the Roman Empire but was not used by the Romans as such.

Source: Wikipedia — Borders of the Roman Empire (CC BY-SA 4.0)