The first thing you see in the old town of Regensburg is stone. The Steinerne Brucke, the stone bridge, was built in the twelfth century and was for hundreds of years the only bridge across the Danube for a long distance, so trade routes ran through the city. It made the town rich, and the merchants built tall towers and patrician houses in the streets by the river. The whole old town survived the Second World War almost untouched and was listed by UNESCO in 2006.
Below the medieval layers lies the Roman fortress of Castra Regina, and walking the streets, you can feel the earlier plan. The old city centre is a dense grid, narrow lanes and open squares, and some of the straight streets follow the lines of the Roman camp. The Romans left walls, gates and a few reused stones, and the Porta Praetoria is the best-known fragment. After the Romans left, Bavarian dukes ruled from here, and later, between 1663 and 1806, the Imperial Diet sat in the city.
The cathedral, with its twin spires, is the great Gothic landmark, and it is the home of the Domspatzen, a boys' choir that is nearly a thousand years old. The old town has more than a thousand listed buildings, and cafes and beer gardens everywhere. Regensburg is also known for its sausages, and for a sweet mustard that is served with them. Beer drinkers should try the local Bavarian lagers and wheat beers.
For the rider, the city is compact and friendly, but the old town is largely pedestrian, and cobbles are slippery when wet. Park on the edge and walk, since Regensburg is easy to see on foot. Fuel is easy to find, with stations on the ring roads and in Reinhausen. The Danube cycle path draws cyclists, so take care on the riverside. Spring and autumn are the best seasons, with comfortable temperatures and good light. Evening on the bridge, with the river below, is a fine thing.