The route by the Little St. Bernard is somewhat longer; but after crossing the first Alpine wall that forms the eastern boundary of the Rhone valley, it keeps by the valley of the upper Isere, which stretches from Grenoble by way of Chambery up to the very foot of the Little St. Bernard or, in other words, of the chain of the higher Alps, and is the broadest, most fertile and most populous of all the Alpine valleys.