From rrain station Montroc (bus stop line 1), cross the road to take the Chemin Paul A Ya and then the Chemin du Gragni. Reaching the little bridge over the Arve, cross over and follow the path to the right as far as signpost 103. Leaving the village of Montroc, the trails runs through the two highest villages in the valley, before winding up the alpine pastures of the Charamillon, Balme and Les Posettes by excellent footpaths. The first climb leads below the Lac de Charamillon where it follows a traverse which undulates, but requires only a minimum of attention. At the Col de Balme the trail passes into Swizterland, to wind through the pastureland of Catogne which clings to the foot of the Croix de Fer (which can be incorporated as a round trip). Leaving the chalets, a short, steep slope leads back into France. From here, there is an outstanding view of the Mont Blanc massif. Following a rapid descent onto the Col des Posettes, there is a rolling section with a few false plateaux (gently rising), which offer the opportunity to work on speed. Beneath the Aigette des Posettes, the final descent leads down to Montro via a good path which ends in the forest.