The Danube gorge at Weltenburg is the best reason to ride south from Regensburg. About forty kilometres upstream, the river hits a wall of Jurassic limestone and, instead of turning aside, cuts straight through it in a narrow defile with cliffs on both sides, some of them over a hundred metres high. At the entrance to the gorge sits Weltenburg Abbey, one of the oldest monasteries in Bavaria, founded around 700, with a baroque church by the Asam brothers and a brewery that claims to be the oldest monastery brewery in the world.
You can reach the abbey by road, or by a small boat from Kelheim that takes about thirty minutes through the gorge, and it is a fine trip on a clear day. Above Kelheim stands the Befreiungshalle, the Hall of Liberation, a giant round monument built by King Ludwig I to commemorate the defeat of Napoleon. The Altmuhl joins the Danube at Kelheim, and the roads along both rivers are among the best in the region.
From Regensburg, the road follows the Danube upstream through farmland and small villages, with the river appearing and vanishing between trees. The surface is good and the bends are easy, but traffic is heavy on summer weekends, with cyclists and day trippers. The gorge road itself is narrow and can be slow. In spring, the meadows are bright green, and in autumn the beech forests on the cliffs turn red and gold.
The Roman legionary camp at Regensburg that began this journey lies behind you, and it is worth remembering that the Romans too used the river as a highway and a boundary. The Danube Limes ran along the south bank here, with forts at Abusina, near Eining, a short way upstream of Weltenburg. Regensburg has fuel on every ring road and plenty of cafes, and Reinhausen, across the water, has its own pleasant streets. Fill up before the gorge. Drink a beer in the abbey garden, and watch the boats.