A 58 km cycle path between Velen and Anholt along the Bocholter Aa river.

https://www.borken.de/fileadmin/daten/mandanten/kreisstadt/PDF-Dokumente/Touristik/Flyer_Bocholter_Aa-Radweg_Druckversion_Stand_Mai_2011.pdf

The trail starts in Herrenberg and goes all the way to Castle Hohenentringen and is a part of the long distance hiking trail, named HW5. When you tapped the castle's wall, you doing the same route back to Herrenberg. It is a strenous trail with an altitude of round about 500 meters. Distance is 25,8 kilometers

--submitted by Marcus Muhr

From the USDA's Forest Service website: