Charmant Som from la Diat
Starting point: la Diat Difficulty: 1 Ascent: 1077 m Time: 6½ hrs Quality: ***
The described route takes a full day, taking almost as long to descend as it does to ascend. It begins down at la Diat, the small village below St. Pierre de Chartreuse (map), which means that it's a long way up. But it's a worthwhile day, and it does have the advantage that it's not too far to stagger to a bar on your return. Some of the first hour is spent climbing steep tracks, but most of the ascent is good walking, following a section of the Tour de Chartreuse. The time allows for both ascent and descent.
You can park your car by the Pont Routier de la Dame, which carries the D520b over the Guiers Mort (790 m, grid ref. UTM 31T 71983 50245). On the other side of the road, there is a reassuring sign for the Tour de Chartreuse and Charmant Som. Cross the municipal recreation grounds above the swimming pool and tennis courts, to a path which makes its way through woodland and pasture, to reach a road junction at la Martinière after some 20 minutes. Turn right, and carry along the road for 100 metres to a T-Junction. A steep track rises opposite to an attractive group of houses, and then continues into the forest.
The track continues to rise steeply, but eases after it is joined by another track coming in from the right at 1050 metres. Turn left here, and you soon reach a pasture with a group of barns. Keep right. In another 15 minutes you pass through a second pasture (la Pleynan, 1140 m). Turn right, and the track turns into a path. This soon joins another track, where you need to keep left. Fifty metres later, a path turns off to the right. You are now on your way! This path climbs steadily and easily, for some 45 minutes up beautifully constructed zig-zags, to le Collet (1562 m), a col on the north-east ridge.
Leave le Collet by the path to the left which after 5 minutes passes within 20 m of the entrance to Puit Kriska, at 780 m the deepest cave in Chartreuse, and within about 10 minutes you reach the cliffs on the eastern flanks of Charmant Som. The cliffs here consist of rock folded almost to the vertical, and the path makes its way across these along ledges and up weaknesses for some 20 minutes or so. The Par les Dalles is not difficult, or exposed, but it is a magnificent path in a superb situation and should be lingered over. The views into the valley and across to Chamechaude are spectacular, and the flora in both spring and summer presents a riot of colour.
All good things come to an end, and at 1750 metres you enter the summit pastures with a path joining from the left. This comes from the car park at the end of the road from the col de Porte just fifteen minutes away! Turn right, and follow the well-used path easily up the final slopes to arrive at the summit (1867 m) after a further 20 minutes, some three hours or so from the car park.
There are worse spots to have lunch. The views are splendid. Chamechaude dominates to the south-east, and with a pair of binoculars you can pick out the traverse through the cliffs from le Jardin. To the north, you can see the monastery nestling beneath the dramatic western cliffs of the Grand Som. By moving along the ridge to the north for a few metres, you can get an impression of the splendid cliffs lying beneath you. To the west, you can start to appreciate that Charmant Som is a far more significant topographical feature than it gives the impression of being when seen from the Martinière valley.
Although you can descend by the way you came up, it is recommended that you return by the Valombré valley. which is on the other side of the ridge from the ascent. Return to le Collet, and turn left onto a path descending the northern side of the ridge. After a couple of minutes, there is a distinct junction, with the way to the left descending into the valley. We, however, take the right path which follows an attractive line across open slopes beneath the impressive cliffs of the Arête de Bérard. From here there are good views of the monastery, and we have seen monks walking on this path.
Eventually, the path swings away from the cliffs and descends sweeping zig zags through the forest to the Valombré road. Turn left, and within five minutes you'll find yourself at the junction with the D520b.
You can avoid walking back along the busy main road. Follow the path along the true left bank past the prominent cave entrance of the Résurgence de la Porte de l'Enclos with its charming sculpture, and when it rejoins the main road, a track takes off up the hill to the right. This ascends to a few houses above la Diat. before joining a road. Follow this down, and you'll arrive back at the car in just a few minutes.