Take the D902 to reach the village of Bonneval-sur-Arc. There is a large car park at the end of the Route du Tralenta. A smaller car park is also available near the Vallonnet chairlift, on the Route de l’Écot.
The route starts at the foot of the Vallonnet chairlift.
(S/E) Cross the Blue run “Polo” and start climbing it on the left-hand side. Between the3rd and4th pylons, turn left onto the Green run “Alouette”. There may be signs prohibiting pedestrians. However, tolerance is the order of the day as this is the only possible route, which is also used by the ESF for snowshoe excursions. This is why you are asked to keep to the left of the run and not to walk side-by-side if you are in a group.
(1) Head back up the Green run. In one of its bends, admire the ice waterfall. Continue to the next junction with the Blue “Polo” run.
(2) Ignore the right-hand side of the Blue run “Polo”, which descends back to the village, and continue climbing to the left, following the Blue run “Accenteur” towards the nearby ski lifts. If you wish, stop by the ski patrollers at the Barme T-bar lift (Balme on IGN maps) to get some information.
(3) Cross the Green run, then the Red “Épervier” run, and head towards the Blue “Accenteur” run. Climb this steep slope on the left-hand side until you reach the red safety nets (empty).
(4) Follow the nets, heading left onto the “Chardonneret” run, and you’ll soon reach the Y-junction formed by the Circaète and Chardonneret runs.
(5) Take the trail on the right and leave it very quickly on your right, continuing off-piste. Follow the Vallonnet stream up its right bank, following the ski touring or snowshoe tracks. If recent snowfall has covered all traces, head towards the cirque at the very back, keeping the Glacier Supérieur in your sights, as its summit is visible from a distance. Reach the slight incline marking the proximity of the glacier.
(6) Continue straight on for a few dozen metres until you reach the glacier. The cave is situated in the middle of the vault. Be wary of falling stalactites or blocks of ice that might break loose.
(7) Retrace your steps to the start of the arch. Go round the glacier to the right (on your right-hand side after turning round at the arch = on the left-hand side of the glacier when viewed from the front). Continue the climb for a few dozen metres until you reach the clearly visible opening of a tunnel which you can pass through . The view is magnificent. Also take a moment to admire the Upper Glacier at the summit.
(8) From the glacier tunnel, retrace your steps to the entrance to the vault. Head towards the slight incline you took on the way there.
(6) Do not follow the track from the outward journey, but cross over to the left bank of the Ruisseau du Vallonnet. As it is buried under the snow and therefore invisible, head slightly towards the left-hand walls without getting too close to them. Further on, if there are no tracks, aim for a green and yellow snow-level marker post. Reach the safety nets from the outward journey.
(4) Descend the run towards the Refuge du Criou. Continue along the Green run, which curves slightly to the right a little further on.
(2) At the junction with the Blue run “Polo Village”, follow the green arrow for “Alouette Village”. After several hairpin bends, rejoin the Blue run.
(1) Head to the foot of the chairlift (S/E).