Passau stands at a meeting of three rivers, and the Romans noticed. The Inn, the Danube and the small, dark Ilz flow together under the cathedral hill, and the Inn bank opposite, where the Innstadt lies today, was the site of the Roman fort of Boiotro, which guarded the Danube frontier, the Limes, and commanded the river crossing. The name suggests the Boii, the Celtic people who once lived in this region, and the Roman fort stood in a long line of defences along the river, from here down to Oberranna in Austria.
The old town on the peninsula, at the confluence, is a beauty of baroque facades, narrow lanes and arcades. St Stephen's Cathedral holds one of the largest church organs in the world, with nearly eighteen thousand pipes, and a summer organ concert is a memorable thing. The Veste Oberhaus, a fortress on the hill across the Danube, gives the best view of the three rivers, which the locals say are three colours: the Danube blue, the Inn green and the Ilz black.
Passau is a city of about fifty thousand, with fuel, restaurants and shops all over, though parking in the centre is limited, so use the car parks along the river. Across the border, only a few kilometres away, Austria begins, with the pleasant town of Schärding on the Inn. The student population keeps the cafés lively, and the beer garden culture is strong, with a Bavarian roast and a pretzel the standard fare.
The riding here is a gentle combination of river and forest. The Danube valley road toward Linz is lovely, with wooded hills pressing in on both sides, and the Bavarian Forest rises just to the north, with long climbs and sweeping views. The Danube cycle path is popular, so expect plenty of cyclists in summer. Spring is cool and fresh, while autumn brings fog and amber leaves. Winter floods occasionally cover the riverside streets, so check before you plan to park near the water.