Above the village of Pfünz, on a spur of white Jura limestone looking down into the Altmühl valley, the Romans built a fort they called Vetoniana. Today a reconstructed gate and a stretch of wall stand on the hilltop, and from up there you understand the choice at once: the valley floor curls below you, the river meanders slowly, and anyone moving along it would have been seen hours before they arrived.
The fort belonged to the Raetian section of the Limes, the long frontier that ran from the Rhine to the Danube, and Pfünz guarded the hinterland a little south of the wall itself. Its end was violent. During the Germanic raids of the third century the garrison was overrun, and excavations found clear traces of a sudden attack. Below the fort lay the civil settlement where traders, craftsmen and soldiers' families lived, now just meadows and a few marked outlines. It is a quiet, slightly melancholy place, best visited when nobody else is there, which is most of the time.
The Altmühltal Nature Park is one of the great motorcycling valleys of Bavaria without being famous for it. The road between Eichstätt and Kipfenberg follows the river in long, flowing bends past juniper heaths and pale crags known as the Twelve Apostles further upstream near Solnhofen. Side roads climb out onto the Jura plateau through beech woods and drop back down in tight turns. Watch for cyclists on the valley route, which is one of Germany's most popular bike paths, and for gravel thrown onto the bends by farm traffic. Spring and early autumn are ideal; summer weekends get busy with canoes and campers.
The rock is the thing. This is the same fine-grained limestone that gave the world Archaeopteryx, found in the quarries around Solnhofen and Eichstätt, and you can see fossils in the museum at the Willibaldsburg, the fortress above Eichstätt. The town itself, five kilometres away, is the obvious place for fuel and lunch: a compact baroque bishop's seat with a cathedral, a university, plenty of beer gardens and the honey-coloured squares the Italian-trained architects left behind after the Thirty Years War. Fill up there, because Pfünz itself is a village with a church and not much else.