The ruins of this military camp can be seen outside Visegrád, to the north, on a hill that overlooks the Danube. The camp has a triangular ground plan. It was built in the first half of the 4th century as one of the important fortifications along the limes, the frontier of the Roman Empire. Its praetorium (the commander’s building) was constructed at the end of the 4th century. In the early 5th century, the Roman army abandoned the military camp. In the 10th and 11th centuries, the fortification, rebuilt as a castle, became a regional centre of the recently formed Hungarian state. “Visegrád” appears for the first time as the name of this regional centre (1009). The fortification was finally destroyed in 1242 by the Mongol invasion of Europe.