Park at the “Pont des Allemands” (819m), 500m after leaving the road from Saint-Laurent-du-Pont to Saint-Pierre de Chartreuse at Pont Saint-Pierre, heading towards La Correrie.
(S/E) Take the only unpaved track that climbs to the south-west. It ascends the hillside then levels out, skirting the terrain until it turns north as it approaches a stream. Cross it and follow the path on the right bank for about a hundred metres, then turn right onto the sloping meadow of Chartroussette, staying on the edge of the forest. As you approach a white-panelled livestock building, take a path down to the right towards Habert de Chartroussette, visible through the branches.
(1) Take either the meadow that leads uphill or (marked route) the path that heads north-east and climbs up to the tarmac summer road. Follow this to the left until you reach a wide left-hand bend in the mountain pasture.
(2) From there, two ascent routes are possible (the trail follows the second):
- climb up the north-facing meadow and veer left to ascend through the forest directly to Corde.
- continue along the level road, passing the livestock building visible from below. After entering the forest and a right-hand bend, take the path that climbs diagonally to the right up to the Habert des Rochers.
(3) Behind the habert, take the Essart des Rochers path, which climbs steadily up to the Corde meadow, where you can see the ruins of the habert on the right.
(4) Continue climbing across the Corde meadow until you reach the edge of the slope beneath the Rochers de Montheur. Begin the descent beneath these rocks until you come to the foot of the Belvédère d’Arpison, a rock clearly visible higher up on the left.
From there, climb up the steep gully towards the north-east between very steep slopes and only veer left once you can see the ridge, which you reach at a broad saddle overlooking the Arpison meadow.
Note: for this entire section, see the Practical Information.
(5) Descend easily, following the view, towards the meadow and its cross-country ski tracks.
You can make a round trip to the Arpison viewpoint by heading to the south-western edge of the meadow and climbing a few dozen metres into the woods.
Alternatively, head right along the edge of the meadow, pass above the Habert d'Arpison and join the path on the right which climbs through the forest towards the south-east to the Col d'Arpison.
(6) Cross over to the other side. After two bends, the path emerges from the forest; leave it to descend straight down the slope of the meadow leading to La Cerna. The path rejoins the forest and heads left towards Billon, heading north-east. On leaving the forest, head for the beautiful building at Habert de Billon.
(7) Head north-east across the mountain pasture, following a series of ascents and flat sections that take you across the Prairie de la Folie; then, after a brief descent through a wood, climb up to the Col de la Ruchère.
(8) Descend due south over a grassy ridge and then down the slope to a path entering the forest. This leads down to the main path coming from Bovinant, which you take to the right. Several routes are possible: each time, take the one branching off to the right to descend more quickly towards the south-west. Towards the bottom of the valley, turn right when you see buildings in the forest to reach the Chapel of Notre-Dame de Casalibus.
(9) Take a detour to the right to the Chapel of Saint-Bruno perched on its rock, then turn back to take the level path heading south-west. Avoid the wide circular loop formed by the forest road by taking a shortcut down to the right leading to the Ruisseau de Saint-Bruno, at the bend where the forest road crosses it.
Follow this stony forest track down alongside the stream, pass a water reservoir and emerge onto the summer road coming from Chartroussette, near the sawmill and then the Grande Chartreuse Monastery.
(10) Follow the snow-cleared road of La Correrie down alongside the monastery wall and, after another reservoir, take the road (usually snow-covered) that branches off to the right and descends the right bank of the Ruisseau de Saint-Bruno to the Pont des Allemands (S/E).