The Aschauer Ache rises at the foot of the Großer Rettenstein and then flows to Kirchberg, continuing to Reith bei Kitzbühel before discharging into the Kitzbühler Ache near St. Johann in Tirol.
The Rettenstein lies in the Spertental-Rettenstein protected landscape and so Pine, Spruce, Gentian, Willow Gentian, Platenigl, Edelweiss, Monkshood, Rock Ptarmigan, Black Grouse and Capercaillie, Red Deer, Chamois, Ibex and Marmot all occur here.