Where is the German Rail Pass valid?
Your German Rail Pass is valid on all trains within Germany operated by Deutsche Bahn (DB). You can also travel to the border cities, Basel in Switzerland and Salzburg in Austria.
Futhermore you can use local trains operated by various private railway companies (PDF file).
Seat reservations are mandatory on night trains and recommended on ICE high-speed trains.
The German Rail Pass can also be used for some free or discounted travel by bus or boat, see the pass bonuses.
The German Rail Pass is not valid on the DB Urlaubsexpress and the DB Autozug (car train).
For international trains that cross the German border you need to buy a supplement for the non-German part of the route.