If you want hills then you could always come to Bavaria. Heading south from Munich gets you into the edge of the alps and there are some nice routes with everything from rolling hills to full alpine passes.

The ADFC has information for cyclists although I'm afraid it's all in German and they publish some good cycling maps.

Another thing to know is that most regional trains have bike racks or even bike carriages, so it's quite easy to get around with your bike.