 Its watercourse, la Dranse de Ferret, flows northwards to join the Rhône at Martigny.The borders of all three countries converge at a tripoint near the summit of Mont Dolent at an altitude of .From here the French – Italian border runs southwestwards along a ridge of high summits on the southern side of the massif, many of which are over in height, including the Grandes Jorasses, Rochefort Ridge, Dent du Géant, Mont Maudit, Mont Blanc and its western satellite, the Aiguille de Bionnassay.