The River Vartry rises on the slopes of Djouce mountain. Nearby, the River Dargle rises between Tonduff and War Hill, falling as the Powerscourt Waterfall, Ireland's tallest waterfall at , over a cliff formed by a glacier at the contact point between the granite and mica-schist of the Wicklow Mountains. The waterfalls at the heads of the valleys of Glendalough, Glenmacnass and Glendasan also occur approximately at the schist-granite junctions, as does the Carrawaystick waterfall in Glenmalure.