This tour starts in Triemli, and goes along the Reppischtal to Albis, where it turns back to the start. The Wildnispark Sihlwald has now banned many trails for biking. There were some paths, where you can bike, but those weren't interesting.
In Langnau-Gattikon the trail would go along the Sihl, but it's now closed. So... I decided to end the tour here, and took the train back home.