Reichenau, Switzerland in the context of Oberalp Pass

The Alpine Rhine Valley (German: Alpenrheintal) is a glacial alpine valley, formed by the Alpine Rhine (German: Alpenrhein [ˈalpm̩ʁaɪn] ), the part of the Rhine between the confluence of the Anterior Rhine and Posterior Rhine at Reichenau and Lake Constance. It covers three countries, with sections of the river demarcating the borders between Austria and Switzerland and between Liechtenstein and Switzerland. The valley is 93 km long. In the upper 9 km stretch, the valley width is 1.5 km with narrow (60 m) incised channel. For the next 71 km, the valley floor varies between 3 and 4 km; on approach to Lake Constance the valley widens up to 15 km.

The Hinterrhein (German: [ˈhɪntɐˌʁaɪn] ; Sutsilvan: Ragn Posteriur; Sursilvan: Rein Posteriur; Rumantsch Grischun, Vallader, and Puter: Rain Posteriur; Surmiran: Ragn posteriour; Italian: Reno Posteriore), or Posterior Rhine, is the right of the two initial tributaries of the Rhine (the other being the Vorderrhein). It is located in the canton of Grisons (Graubünden), Switzerland. One of its upper tributaries is Reno di Lei, which is the outflow of Lago di Lei located in Lombardy, Italy.

Although it is shorter in length, its volume is larger than that of the Vorderrhein at their confluence near Reichenau, after which the river is called the Alpine Rhine, which flows out into Lake Constance (Bodensee).