The Belledonne range is approximately long by between wide and runs from roughly , south-south-east of the city of
Grenoble, in a north-easterly direction (actually 35 degrees) for to roughly , near the town of
Aiguebelle. The highest point is the
Grand Pic de Belledonne, . The range is delineated by several valleys which lie at relatively low altitude, including the
Grésivaudan Valley (which carries the
Isère) on the west, the river
Arc to the north and the
Romanche to the south. The range counts dozens of peaks over , more than 10
glaciers, and many alpine lakes, the highest of which is over above sea level. Geologically, Belledonne is a concatenation of ranges which are not physically separated; from north to south, these are: the Grand Arc, the Lauzière, the Sept-Laux, Belledonne proper, and the Taillefer. Belledonne is a
crystalline range. It initiated as a
Paleozoic peneplain which was covered by
Mesozoic sediments, then raised and tilted during the Tertiary uplift of the Alps and subjected to glacial erosion during the
Quaternary. As a result of its geologic history, Belledonne alternates jagged peaks with gentle slopes. Belledonne overlooks the fairly flat Isère Valley () which lies only above sea level near Grenoble. Hence, all alpine vegetation zones are represented: • Hill zone: coppices of
Downy oak on South facing slopes (),
hornbeam, common maple. •
Montane zone: beech, birch, aspen, English oak, sycamore maple, goat willow, then fir and spruce. •
Subalpine zone: moors and sparse stands of spruce, mugho pine, stone pine, and silver birch. •
Alpine zone: grassland, scree and rock. Before the automobile era, locals frequently used this pass to go from Gresivaudan to the Eau d'Olle valley, or to continue to the
Maurienne valley via the
Glandon pass.
Hannibal may have passed the Pas de la Coche when he crossed the Alps with his army.
Main lakes Belledonne and its lakes have played a major role in industrializing
hydroelectricity production as early as 1869 thanks to pioneer
Aristide Bergès and his paper mills which tapped water from lake Crozet. ==Ski resorts==