Start from St-Véran. At the south-east end of the village, take the road to the Clausis chapel. After a 3 km climb, there's a small parking lot and the Château Renard observatory trail on the left. This is the place to go up.
At 2650 m, below the bars, in a left-hand hairpin bend, a path leads off to the right towards the Col du Longet (2701 m).
To make the most of it (d+/- 281 m): return to the observatory of the Château-Renard peak (2931 m, the highest point for mountain biking) and on foot to the peak itself (2989 m).
Fun descent of the Longet valley. At the bottom of the Lariane bridge, stay on the left bank to pass in front of Fontgillarde and Pierre-Grosse, and climb back up to the left along the Bois des Amoureux forest road towards St Véran.