Biking is one of the favorite activities of the Germans. Some families seem to be centering their entire life around the bicycle with the kids biking to school, familiy biking tours, bike races...
There is a quite a few nice places to go biking near Aachen.
- There is some decent spots in Aachener Wald
- Vennbahnweg: The Vennbahnweg is a bike trail which starts in Aachen and goes all the way down to Luxembourg. If you don't feel like biking all the 130km to Luxembourg, you can just go to one of the many stops on the way down (e.g. Kornelimuenster).