La Ruinette is a mountain of the Swiss Pennine Alps , overlooking the Lake of Mauvoisin in the canton of Valais . With an altitude of 3,875 metres above sea level, it is the highest summit between the Grand Combin and the Dent Blanche . La Ruinette lies close to the better known Mont Blanc de Cheilon which has almost the same height (3,870 m).