The Side valleys of the Lech Valley owe their present appearance to the glaciers of the ice ages. The ice of the mighty Lech Glacier (origin: Würm, catchment area: northern Limestone Alps, connection with other glaciers: ice from the Central Alps with crystalline debris, extent: several kilometres wide and over 600 m thick) formed the valley system into a striking trough valley. It blocked the smaller glaciers of the side valleys, creating hanging valleys above the main valley. This formed impressive gorges or waterfalls at the exit of the side valleys. They are mostly inaccessible and therefore refuges for many animals and plants. The streams of the side valleys play a special role for the Tyrolean Lech. They are important lifelines as they supply the wild river with water and valuable bedload.