The Altmühl Valley sits close to the line of the ancient Roman frontier, the Limes Germanicus, which runs through the region from northwest to southeast. Several watchtower foundations and reconstructed sections of the fortified frontier wall can be visited along the valley's edges, most accessibly near the village of Weissenburg, just north of the valley proper.
The Römisches Museum in Weissenburg has one of the best Roman collections in Bavaria, including a well-preserved Roman bath complex. The frontier itself is a UNESCO World Heritage Site. Cycling or walking the Limes trail is possible over several days; the route is waymarked and connects a string of archaeological sites.