The Sihltal begins in the Alps of the canton of Schwyz. At the Saaspass, which leads from the upper Sihl valley into the Klöntal, there is a Sihlseeli, a small mountain lake that the Sihl does not flow through. With the Sihlsee, a reservoir in the canton of Schwyz, the Sihl is used to generate electricity for the Swiss Federal Railways. Two dams were erected during the construction of the power plant. The Sihltal extends to the gates of the city of Zurich. The villages of Biberbrugg, Sihlbrugg, Langnau am Albis, Adliswil and the natural Sihlwald as well as the Langenberg wildlife park are located in the Sihl valley.
The main Zurich-Zug axis, a continuation of the Gotthard Railway, crosses the Sihl valley at Sihlbrugg Station. There the railway line to Zurich, belonging to the Sihl Valley-Zurich-Uetliberg-Bahn (SZU), branches off. The Sihltal is also developed with a two-lane main road, which was the main connection axis from Zurich to the south (Zug, Arth-Goldau, Gotthard) until the opening of the motorway by the Knonaueramt. The connection to the communities on the left bank of Lake Zurich and to those on the other side of the Albis chain is ensured by various bus routes. The Adliswil – Felsenegg aerial cableway leads from Adliswil to the Felsenegg.