Frontiers of the Roman Empire – The Danube Limes (Western Segment)

The western segment of the Danube Limes covers almost 600 km of the Roman frontier on the Danube, from Bad Gögging in Germany through Austria to Iža in Slovakia. It formed the northern and eastern edge of the provinces of eastern Raetia, Noricum and northern Pannonia, and for more than 400 years from the 1st century CE it was the empire's border in central Europe. Because the river banks were boggy and cut by side channels, no ramparts were built here, unlike on the Neckar-Odenwald Limes in Germany.

The frontier was first laid out as a continuous line under the Flavian emperors (69–96 CE) and was extended later. Camps built in the mid-1st century were at first surrounded only by earth banks; under Trajan they were given stone walls. The system turned on legionary fortresses, one each in Raetia and Noricum and two each in Upper and Lower Pannonia, with forts, fortlets and watchtowers between them and a Pannonian fleet on the river. The oldest Roman camp in Austria was Carnuntum. In the 4th century Valentinian I (364–375) repaired the decaying forts, thickening walls and adding towers.

The western frontier broke down in the 5th century, but many Roman structures became the cores of medieval villages and towns, many of which still exist. In 2021, 77 component parts in Austria, Germany and Slovakia were inscribed.