Pannonian Limes

The Pannonian Limes is that part of the old Roman fortified frontier known as the Danubian Limes that runs for approximately 420 km from the Roman camp of Klosterneuburg in the Vienna Basin in Austria to the castrum in Singidunum in present-day Serbia. The garrisons of these camps protected the Pannonian provinces against attacks from the north from the time of Augustus to the beginning of the 5th century. In places this section of the Roman limes also crossed the river into the territory of the barbarians.

Source: Wikipedia