The Grand Som loop via the south ridge and the Monastère de la Gde Charteuse

By car: take the D520b then the D103 to the Musée de la Grande Chartreuse, situated at a place called La Correrie, in the commune of Saint-Pierre-de-Chartreuse, on Route du Désert. Do not park in the museum car park but before the entrance; take the forest track on the left which leads to the hikers’ car park.
(S/E) From the car park (alt. 870 m), continue along the forest track for about a hundred metres (south-east).

(1) At the first bend, leave the track and follow the ‘Tour de la Chartreuse’ path to the right (south-east), which is signposted (yellow and white/red) and marked by an old wooden sign reading ‘Grand Som’. The path curves round and then climbs (north) to join a wide track (alt. 950 m). Follow it up on the right for about 150 metres (east).

(2) Leave the track (Alt. 970 m) and follow the path to the left (marked yellow and white/red). This shortcut climbs (north-east) and, after a few hairpin bends, rejoins the track (Alt. 1010 m). Follow it up on the left; 500 m further on, it continues as a path (marked yellow and white/red). At around (alt. 1,120 m), it descends gently for about 150 m, passing a path on its right, and shortly afterwards joins a track (alt. 1,100 m).

(3) Take this track, which is almost level, to the right. It heads north and, after about 300 m, meets an ascending path, running almost parallel to it on the right.

(4) Leave the track and take this path, which is still signposted (yellow and white/red). It climbs in a straight line, then winds its way up, becoming less steep. After about 100 m of level ground, at an altitude of 1,180 m, look out for a path on the right heading uphill in the opposite direction, which begins with a rocky step. It is marked by a cairn and two crosses (Yellow Cross and white/red) on a tree.

(5) Follow this path, which is very rarely marked with small pink dots, but its well-defined trail is easy to follow, especially as it does not cross any other paths. It climbs a steep slope in a series of hairpin bends to reach a junction on the ridge (elevation 1,552).

(6) The path on the right immediately ends in a dead end. Turn left (north) onto the path that follows the ridge northwards. Shortly afterwards, at an altitude of 1,600 m, the path meets the one coming up from Saint-Pierre-de-Chartreuse.

(7) The signpost indicates the Pas de la Suiffière. Follow this direction (north-east). Now marked (yellow), the path crosses the Col du Frenay then continues its ascent, winding its way through dense vegetation from which it emerges with difficulty, crosses a woodland and reaches a vast scree slope. It winds its way up the scree slope, skirting the Suiffière cliff on the right. Photo: The Suiffière cliff. Continue northwards to reach a fork at an altitude of 1,770 m.

(8) Leave the path that heads straight on (north) and take the marked path (yellow) to the right. It winds upwards towards the cliff (north-east), then veers off (south), leaving a path on the left (north) at the bend. Climb a few rocky steps and, via a near-level traverse, reach the Pas de La Suiffière.

(9) The Pas de La Suiffière is not, strictly speaking, a climb, but rather a short scramble, provided you follow the yellow markings which make use of a gap in the rock barrier to reach the eastern slope.

(10) At the top of the pass, you have a choice:
1) Either descend a few metres to take an easier path joining the Racape path which leads up to the Grand Som. This route is recommended for those who have encountered some difficulties or felt apprehensive on the Pas de La Suiffière.
2) Alternatively, climb the southern ridge, as indicated by the title of this walk and shown on the map. Along the ridge, follow as best you can the faded red arrows or lines, which are not always visible. There is a pleasant scramble along the Grand Som ridge, covering approximately 200 metres of elevation gain and 600 metres in length, with no technical difficulty but featuring some very exposed sections.

(11) From the summit of the Grand Som (2,026 m), take the sheep track (yellow) heading north. It descends gently through the mountain pastures on the eastern slope and reaches a Fork in the road.

(12) Leave the Bovinant trail on your left – access to this route is prohibited – and continue along the path to the right. It descends steeply through scree and over a sharp limestone pavement, where you’ll need to choose your footing carefully to avoid slipping and sliding.

(13) Cross a gap (alt. 1,800 m) and move onto the western slope. After 50 m, you’ll come to a fork; ignore the path on the right and follow the one on the left (marked yellow). The descent continues (northwards) along a gullied and often muddy path. Heading west, it tackles the slope head-on and crosses a rocky ridge via two fissures. After this section, head north again to reach the Col de Bovinant (elevation 1,646 m).

(14) Turn left and head south: ‘Tour de la Chartreuse’ (yellow/red). Note that you can bypass the pass by taking a shortcut 50 metres before it. The path passes Habert de Bovinant and winds down into a small valley . Photo: View from Habert de Bovinant. On a stony plateau, you’ll come to a junction.

(15) At the signpost, leave the Col de La Ruchère via the Pas du Loup on your right and continue the descent straight ahead for about 500 metres

(16) At the next signpost, ‘Sur Bourdoire’, ignore the GR®9 sign for ‘La Correrie’ on the left and take the yellow-marked path on the right towards ‘Bourdoire’. After a further 150 m, you’ll come to a junction marked by a cairn.

(17) Head down the marked path (yellow) to the left.

(18) At the “Bourdoire” sign, follow the sign for “Le Réservoir” (yellow) to the right. After about a hundred metres, you’ll come to another “Bourdoire” sign. Continue in the direction of “Le Réservoir” to the left (south-west) until you reach a junction. Ignore the straight shortcut to the left and turn right towards Notre-Dame de Casalibus.

(19) Leave Notre-Dame de Casalibus via the south-south-westerly path. You will reach a large clearing where three forest tracks meet. Ignore the track straight ahead and turn onto the one on the right, marked in yellow. It forms a Z-shape, crossing and then running alongside the Ruisseau de Saint-Bruno. At the sign for “Le Réservoir”, do not take the path on the right towards Habert de Billon; instead, stay on the track straight ahead (south) to reach the Monastery of La Grande Chartreuse. Photo: The Monastery of La Grande Chartreuse. At the end of the monastery, the road forks. Take the left-hand branch; after about 1.5 km, you will reach the car park (S/E).

Marking the route
Marked route from (1) to (5).
Vague and rare paint marks from (5) to (7).
Marked from (7) to (10).
Faded red arrows and markings from (10) to (11).
Signposted from (11) to (E).

Warning: this route has some overhead passages. It is not recommended for people who are prone to vertigo or who have no experience of easy climbing (maximum rating 3).

• The panorama of the Alps from Grand Som is superb. The concrete orientation tables in relief, although in poor condition, make it easy to spot the surrounding peaks.

• Lost in the woods, Notre-Dame de Casalibus is a pretty chapel well worth a visit.

• The Grande Chartreuse monastery on the route is not open to visitors. It is a magnificent complex of buildings with remarkable roofs, estimated to cover 4 hectares. Imposing in height and with steep slopes, they are mostly covered in slate and adorned with numerous dormer windows.

• The Grande Chartreuse Museum, located below the car park, traces the history of this monastic order from a religious, material and architectural perspective. For opening times and dates, phone 04 76 88 60 45.