Get on, get off, simply arrive - an InterCity train runs daily from Stuttgart directly to Oberstdorf in the Allgäu region. On Saturdays, you can travel to Garmisch-Partenkirchen on an ICE train from Dortmund via Frankfurt and Nuremberg. The Chiemgau and Berchtesgaden can be reached by InterCity from Hamburg via Kassel and Würzburg without changing trains. There are also direct connections from Frankfurt/Main to Regensburg and Passau - every 2 hours by ICE. By the way, there is also a daily direct ICE train to the Danube Valley from Hamburg via Hanover and from Berlin via Halle(Saale).