The origin of the Rein da Maighels is the Maghels Glacier () on the Piz Ravetsch near the point where the cantons of Graubünden, Ticino and Uri meet. From the glacier, the Rein da Maighels flows north, through the Val da Maighels, then east, through Val Platta' between Piz Cavradi and Piz Piogn Crap, then into Val Curnera and into the Lai da Curnera reservoir.