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, located at La Correrie, in the commune of Saint-Pierre-de-Chartreuse, Route du Désert. Do not park in the museum car park, but before the entrance; take the forest road on the left that leads to the hikers' car park.
(S/E) From the car park (Alt. 870 m), continue along the forest road for around 100 metres (south-east).

(1) At the first bend in the road, leave the path and follow the Tour de la Chartreuse footpath to the right (south-east), signposted (yellow and white/red), with an old wooden "Grand Som" sign. It bends round and then rises (north) to reach a wide track (Alt. 950 m). Follow it up to the right for about 150 m (east).

(2) Leave the track (Alt. 970 m) and follow the path to the left (Yellow and White/Red). This shortcut climbs (north-east) and after a few hairpin bends rejoins the track (Alt. 1010 m). Go back up to the left and 500 m further on it becomes a path (Yellow and White/Red). At around (Alt. 1120 m) it descends gently for around 150 m, leaving a path on its right, and shortly afterwards meets a track (Alt. 1100 m).

(3) Take this track, which is almost level, on the right. It heads north and after about 300 m meets a rising path that runs almost parallel to the right.

(4) Leave the track for this path, which is always marked (Yellow and White/Red). It climbs straight up, then twists and turns and becomes gentler. After about 100 m of false flat, at around Alt. 1180 m, notice on the right a path going the wrong way up which begins with a rocky step. It is marked by a cairn and 2 crosses (Yellow and White/Red) on a tree.

(5) Follow this path, which is very rarely marked with small pink dots, but its well-marked track is easy to follow, especially as it does not cross any other paths. It twists and turns up a steep slope to reach a junction on the ridge (elevation 1552).

(6) The path on the right immediately dead-ends. Turn left (north) onto the path that follows the ridge northwards. Shortly afterwards, at around 1600 m, the path meets the path leading up from Saint-Pierre-de-Chartreuse.

(7) The sign indicates Pas de la Suiffière. Follow this direction (north-east). Now signposted (yellow), the path crosses the Col du Frenay and then continues to climb, winding through invasive vegetation from which it emerges with difficulty, crosses a wood and approaches a vast scree slope. It winds its way up the slope, skirting the Suiffière cliff on the right. Photo: The Suiffière cliff . Continue north to find a fork at around Alt. 1770 m.

(8) Leave the path heading straight ahead (north) and turn right onto the signposted path (yellow). It winds its way up towards the cliff (north-east), then bends (south), leaving a path on the left (north) as it bends. Climb some rocky steps and, by crossing almost level ground, approach the Pas de La Suiffière.

(9) The Pas de La Suiffière is not, strictly speaking, a climb, but a climb provided you follow the yellow markings which use a weakness in the rocky bar to access the eastern slope.

(10) At the top of the pitch, you have two options:
1) Either descend a few metres to take an easier path that joins the Racape path up to the Grand Som. This route is recommended for those who had some difficulty or apprehension on the Pas de La Suiffière.
2) Alternatively, climb the South ridge, as described in the title of this hike and as shown on the map. From the ridge, follow the faded traces of red arrows or lines that are not always visible. The Grand Som ridge is a pleasant climb, about 200m in height difference and 600m long, with no technical difficulties but some very airy sections.

(11) From the summit of the Grand Som (elevation 2026), take the sheep trail (yellow) to the north. It descends gently into the mountain pastures on the eastern slope and reaches a fork in the path.

(12) Leave the Bovinant path on the left, where it is forbidden to walk, and continue along the path to the right. It tumbles over scree and sharp limestone pavement, where you need to anticipate your footing to avoid slipping and sliding.

(13) Cross a gap (Alt. 1800 m) and switch to the western slope. After 50 m there is a fork in the path, leave the path on the right and follow the one on the left (yellow). The descent continues (north) on a gullied and often muddy path. Heading west, it enters the head-on slope and crosses a rocky bar via two faults. After this passage, head north again to reach the Col de Bovinant (elevation 1646).

(14) Turn left, heading south: "Tour de la Chartreuse" (Yellow/Red). Note that you can bypass the pass by taking a shortcut 50 m before it. The path passes Habert de Bovinant and twists down into a valley Photo: View from Habert de Bovinant. There is a junction on a stony plateau.

(15) At the signpost, turn right for the Col de La Ruchère via the Pas du Loup and continue downhill for around 500 m.

(16) At the next signpost, "Sur Bourdoire", ignore the GR®9 "La Correrie" sign on the left and turn right onto the yellow path signposted "Bourdoire". After another 150 m, come to a crossroads marked with a cairn.

(17) Go left down the (yellow) signposted path.

(18) At the "Bourdoire" sign, turn right and follow the signs for "Le Réservoir" (yellow). After a hundred metres or so, there is another sign for "Bourdoire". Keep left towards "Le Réservoir" (south-west) and come to an intersection. Leave the straight shortcut on the left and turn right towards Notre-Dame de Casalibus.

(19) Leave Notre-Dame de Casalibus on the south-south-west path. You will come to a wide area where three forest roads meet. Ignore the road opposite and turn right onto the yellow signposted road. It makes a Z that crosses, then runs alongside the Ruisseau de Saint-Bruno. At the "Le Réservoir" sign, turn off the path to the right towards the Habert de Billon and stay on the track opposite (south) to reach the Monastère de la Grande Chartreuse. Photo: The Grande Chartreuse monastery . At the end of the monastery, the road forks. After about 1.5 km, take the left-hand branch to 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.