Allow 30 minutes by car from Digne. Head to the hamlet of Les Dourbes, 8 km east of Digne-les-Bains via the D19.
Then continue along the road to the car park at the Maison Forestière du Serre, 1.5 km east of the hamlet.
(S/E) From the car park, follow the forest track south-east to a crossroads.
(1) Turn left to join the Grande Traversée des Préalpes (GTPA) route. A little further up, take the hairpin bend to the right onto a small path which leads up to a track. Follow it to the right and you will reach the path leading to the Pas de Tartonne.
(2) Continue straight ahead along the forest track, which climbs almost straight up alongside the Barre des Dourbes.
(3) Leave the track and head down to the left onto the grassy path. Numerous small channels.
(4) Go and admire the Pierre Saint-Martin, a large rock associated with the Trou de Saint-Martin, situated on the Barre near the Pas de Tartonne. After the trees, you’ll reach woods, then meadows and tree-lined paths. Head down towards the south-west to return to the car park (S/E).