Route with some height difference on the first 10km, can easily be shorted by truning back to the start when getting back to Villigen. Folllow the "wanderweg" in Villigen to Greissberg, enjoy the magnificent view on the top, run towards Mandach (on a small path), do not climb down the steps to the left, but turn rigth a few 100 metres later back to the road to VIlligen. One could turn back to the PSI from here (save 5km).  The route is flat , on nice countryroads/ or well-contained paths.