Here the frontier changes character. West of the Franconian lakes the Romans built the Raetian Limes not as a palisade but, in its final form, as a stone wall, a metre or so thick and perhaps three high, running across Middle Franconia toward the Danube. Medieval villagers who found its rubble in their fields had no idea who had built it and called it the Teufelsmauer, the Devil's Wall, which tells you how thoroughly the empire had been forgotten. The watchtowers numbered in this section sat along that wall in the farmland around Pfofeld and Gunzenhausen, close to where the line crosses the Altmühl valley.
The landscape today is softer than the history. Pfofeld is a small village on a low plateau, and just to the north-east lies the Brombachsee, one of the reservoirs built from the 1970s onward to move water from the wet south of Bavaria to the dry north. The result is an unexpected lake district: sailing boats, sandy beaches, cyclists in matching jerseys and, on hot weekends, a fair amount of traffic around the shore roads. Weekday mornings are another story, with mist on the water, herons in the reeds and long empty lanes through pine woods and pasture.
For riding, think flowing rather than technical. The country roads between Pfofeld, Absberg and Gunzenhausen roll over gentle hills with occasional surprisingly tight bends at village entrances, and the surfaces are generally good. Watch for farm machinery in harvest season and for tractors dragging mud onto the tarmac after rain. The Altmühlsee near Gunzenhausen adds more water to the views, and the Altmühl valley further south becomes properly dramatic with limestone cliffs, if you have time to extend the day.
Gunzenhausen is the practical anchor: a town of some sixteen thousand with fuel, supermarkets and an old centre where a few stretches of the medieval walls survive. Franconian food is hearty and cheap by German standards, so a plate of Schäufele with dumplings and a local beer is a fine reward for the end of a ride, provided someone else is doing the riding afterwards. Along the Limes itself, look for the information boards and a reconstructed section or two of wall and tower around Gunzenhausen; they help you picture how the frontier once looked, a pale stone ribbon cutting straight across the fields you have been riding through all afternoon.