I don't know where you'll be entering Germany, but I really like the Mozel valley (Trier (south) to Koblenz (north)). Try a stop in Cochem.
To me, Germany is getting better and better for each visit. Earlier, I just passed thru using the Autobahn as a tool to reach southern france, spain and italy. The people are nice and the food is good too.
German trains are taking bikes and bikers so you can sleep thru half of europe too - if you're tired or want to wake up after a nice rest in a new country.
In Cochem, you are not too far from the famous Nürburgring - but be careful if you take it for a spin - tourists have a habit of trying to lower Dahnes lap records on their first attempt = fatal outcome - believe me.
have a nice one!