The Altmühl valley in Bavaria is one of Germany's best kept riding secrets, a winding river valley cut deep into Jurassic limestone, lined with juniper heaths, rock towers and castles. Near where the valley meets the Danube, the Roman frontier, the Raetian Limes, ran across the land, and the stretch of watchtowers and small forts numbered WP 15/11 to 15/26 lies in the wooded hills here, between Riedenburg, Dietfurt and the Danube town of Vohburg.
The Raetian Limes was a continuous barrier, at first a wooden palisade and later a stone wall, running across southern Germany to the Danube, where it ended near Eining. Watchtowers stood along it at regular intervals, and soldiers in them could signal to each other and to the forts behind. Today, most of what survives is in the form of low earthworks, foundations and lines in the forest, sometimes with a reconstructed tower or information board. The frontier is part of the UNESCO Frontiers of the Roman Empire site. It is a place for the imagination as much as the eyes.
The riding is lovely in a relaxed way. The roads along the Altmühl between Riedenburg, Dietfurt and Kelheim follow the river through the valley with gentle bends and views of cliffs and castles. Riedenburg has three castles on the heights above it, including Rosenburg, which has a falconry show. Side roads climb out of the valley onto the Jura plateau, crossing forests and fields with long curves and very little traffic. Surfaces are generally excellent, as you would expect in Bavaria, but watch out for cyclists on the valley roads in summer, when the Altmühltal cycle path is busy.
Riedenburg, about eleven kilometres away, has fuel, cafés and restaurants. Dietfurt is famous for an odd local custom: it calls itself Bavarian China, and its carnival includes a Chinese-themed parade. The Bavarian beer gardens around here are the obvious place for lunch, with a roast pork and a dark beer. Autumn, when the beech woods turn and mist lingers in the valley, is beautiful but sometimes chilly in the mornings.