Passau is a picturesque Bavarian city in southeastern Germany, built at the confluence of the Danube, Inn and Ilz rivers right at the Austrian border, and although Passau has no airport of its own - its transport code belongs to the city's rail station rather than any airfield - renting a car here is simple, with desks in the city center and near the main train station serving the steady flow of river-cruise passengers and cyclists who use Passau as a starting or ending point. Most air travelers connect through Munich Airport, roughly two hours west by road, or the smaller Salzburg Airport just across the Austrian border, both practical alternates for reaching Passau by car.
From Passau, the A3 autobahn runs west toward Regensburg and Nuremberg and continues on toward Munich and Frankfurt, a fast, well-maintained route typical of the German motorway network. Cross into Austria and the character of the roads changes: Austrian motorways require a vignette, a prepaid toll sticker or digital pass purchased before use, so anyone planning to drive on toward Linz, Salzburg or Vienna needs to arrange one at the border or a filling station beforehand, since driving without one risks a substantial fine.
Driving is on the right throughout Germany and Austria, and roads immediately around Passau's hilly old town are narrow, cobbled and often pedestrianized, so many visitors park just outside the historic core rather than attempting to drive into it directly. The surrounding Bavarian Forest region brings winding, hilly rural roads and, in winter, snow and ice at higher elevations, making winter tires a sensible precaution for a Passau-based trip between November and March, particularly for anyone continuing on toward the Austrian mountains or the higher stretches of the Bavarian Forest itself. Many travelers use Passau as a convenient stop between Munich and Vienna, breaking up a longer central European road trip with a night in the old town.