The tributary of what river is Lech?

The Lech is a river in Austria and Germany. It is a right tributary of the Danube 255 kilometres (158 mi). Its source is located in the Austrian state of Vorarlberg, where the river rises from lake Formarinsee in the Alps at an altitude of 1,870 metres (6,120 ft). It is not navigable, owing to its torrential character and the gravel beds which choke its channel. There are extensive views of the Lech valley from Neuschwanstein Castle, near Füssen.