Grand Som
The Grand Som is a mountain of the Chartreuse Mountains in the French Prealps, in Isère, France. It has a long ridge, unevenly sharp, overlooking the Petit Som, the Col de la Ruchère northwest and the Grande Chartreuse monastery below the cliffs. The summit has a cross and two relief tables. It lies in the Parc Naturel Régional de la Chartreuse.Caving
Many chasms are present on the massif: Trou Lisse à Combonne, puits de l'Écho, gouffre Roland, gouffre de Mauvernay, gouffre des Aures, but the most important network is the puits Francis or of 723 meters deep for 6,836 m of development. Discovered in July 1966 by the caving club of La Tronche, the siphon at was reached on August 23, 1967. Upper entries were then found.