One of the most prominent Alpine ranges, the Bernese Alps extend from the gorge of Saint-Maurice, through which the Rhône finds its way to Lake Geneva, to the Grimsel Pass or, depending on the definition, to the river Reuss (thus including the Uri Alps). The principal ridge, a chain that runs from west (Dent de Morcles) to east (Sidelhorn), whose highest peak is the Finsteraarhorn, forms the watershed between the cantons of Bern and Valais. Except for the westernmost part, it is also the watershed between the Rhine (North Sea) and the Rhône (Mediterranean Sea). This chain is not centered inside the range but lies close (10 to 15 km) to the Rhône on the south. This makes a large difference between the south, where the lateral short valleys descend abruptly into the deep trench forming the valley of the Rhône and the north, where the Bernese Alps extends through a great part of the canton of Bern (Bernese Oberland), throwing out branches to the west into the adjoining cantons of Vaud and Fribourg. There the mountains progressively become lower and disappear into the hilly Swiss Plateau.