Its valley (the ) forms the boundary between the Zillertal Alps in the west and the Venediger Group in the east, which belong to the High Tauern. The valley begins above the village of Krimml at the Krimml Waterfalls and runs up to its head at the on the mountain of Dreiherrenspitze ( m (AA)). The Krimmler Ache itself rises at a height of about at the to the valley Obersulzbachtal at the east.