Inn

Inn (ancient Aenus), river in central Europe, flowing in Switzerland, Austria, and Germany. It rises in Lake Lughino in eastern Switzerland and flows generally north-east to the Danube. From its source the Inn flows through the Swiss valley of the Engadine, enters Austria near Nauders, and crosses the Tirol (Tyrol) and Bavaria regions. The river joins the Danube at Passau, Germany. In the last part of its course of about 515 km (320 mi), the Inn forms the boundary between Germany and Austria. The principal tributary is the Salzach River.