The Gotthardreuss rises in the Gotthard massif, emerging from Lago di Lucendro (reservoir built in 1947; elevation 2,134 m) in the canton of Ticino and passing into the canton of Uri at Brüggboden (1,910 m).

The Furkareuss rises east of Furka Pass from Schwärziseeli and forms the valley called Urseren, passing Realp at 1,540 m.

Gotthardreuss and Furkareuss join at Hospental (1,452 m). Downstream of Andermatt (1,432 m) the Reuss passes through Schöllenen Gorge and under the legendary Devil’s Bridge. At Göschenen (1,102 m) it is joined by the Göschenerreuss. From here it forms the main valley of the canton of Uri, passing below Wassen (840 m), Gurtnellen (711 m), Silenen (500 m), and through Erstfeld (471 m), past Attinghausen and Altdorf (452 m), joining the southernmost part of Lake Lucerne (the Urnersee) at Seedorf (434 m). Source: Wikipedia.