Of these the Dora (called for distinctions sake Dora Riparia), which unites with the greater river just below Turin, has its source in the Mont GenÃ¨vre, and flows past Susa at the foot of the Mont Cenis.
Next comes the Stura, which rises in the glaciers of the Roche Melon; then the Orca, flowing through the Val di Locana; and then the Dora Baltea, one of the greatest of all the Alpine tributaries of the Po, which has its source in the glaciers of Mont Blanc, above Courmayeur, and thence descends through the Val d'Aosta for about 70 m.
Below Aosta also the Dora Baltea receives several considerable tributaries, which descend from the glaciers between Mont Blanc and Monte Rosa.
Below its confluence with the Dora, the Po receives the Sesia, also a large river, which has its source above Alagna at the southern foot of Monte Rosa, and after flowing by Varallo and Vercelli falls into the Po about 14 m.
Above sea-level, on the Dora Baltea at the point where it leaves the mountains.