The walk around the Buzon viaduct via the Oursatas torrent

Take the N85 road on leaving Gap towards Col Bayard and Grenoble. About 1 km after the Varsie roundabout, turn right onto Chemin de Peyre Ossel, just before Camping Alpes Dauphiné. Drive to the end of the road and park near the Vial farm: there are a few spaces along the tarmac road. This is the former route of the railway line that was intended to link Gap to La Mure via the Champsaur.

(S/E) Take the dirt track that climbs through the trees towards Peyre Ossel and the Canal de Gap, heading north-east, ignoring the tarmac cycle route on the right. Climb gently through the fields until you reach a crossroads.

(1) Turn right onto the path through open terrain, heading north-east, to reach the boulder at Peyre Ossel.

(2) Go round the boulder on the right to descend onto a small path which joins the Chemin de Peyre Ossel amongst the trees. After a few metres, take a small path on the left to reach a bridge overlooking the cycle path. Turn left to descend onto the tarmac cycle route, heading north. Follow this shared path and head back up towards the viaduct. Admire the Buzon viaduct, built in the 20th century for the Gap–La Mure railway line but never put into service. Continue until you are running alongside fields and reach a junction.

(3) Turn right onto the path that runs alongside the field, then walk in the shade of the hedges, heading east, until you cross a stream.

(4) Turn right onto the stony path that follows the stream, heading south. Cross over the Oursatas torrent then continue to the right until you reach a bend.

(5) Take the path opposite which climbs alongside the field, heading south-west, ignoring the rest of the path which descends to the south. Continue through the trees to reach another field and look out for a small path on the right, not very obvious amongst the bushes at the edge of the plot.

(6) Follow this path as it enters the forest and descends towards the stream. After about 50 m, turn left (fluorescent green markings) to head down, heading west then south-west. Staying well above the stream, follow the Oursatas stream and its waterfalls, then join it at a crossroads.

(7) Turn right to cross the stream via the small wooden footbridge, then at the next junction, turn left to reach the Buzon stream and cross that too. Then head back up through the woods and after about 200 m, turn left, heading south-west. At the junction, turn left to descend, heading south, and join the Chemin de l’Oratoire.

(8) Turn right onto this path and head north-west until you reach the crossroads at the Vial farm (S/E).

There are no water sources along the route, apart from the Oursatas and Buzon streams.

The route is mostly shaded and presents no particular difficulty, apart from a few sections through the undergrowth (where the slope is sometimes rugged) and crossing the torrents.

Longer alternatives:
- From the hamlet of Les Jaussauds: head up to the Réserve des Manes after Peyre-Ossel, then follow the Gap Canal (elevation gain: 150 m – total time: 2 hours 30 minutes).
- From Gap: possible start at the junction of Rue Villarobert and Rue du Béal, or from the hamlet of Parassac (at the Chemin de Hauteville roundabout). And at the point (8), return via the Chemin de l’Oratoire (elevation gain: 350 m – total time: 3h30).
- Towards Le Jaussauds: at the point (3), continue along the tarmac V64 cycle route to Le Jaussauds. You can then complete a circular route by descending via Serre du Four to reach the point (4) and continue along the original route.

The Peyre Ossel erratic boulder, also known as the “Pierre des oiseaux”, is composed of conglomerate sandstone containing quartz pebbles, fragments of rhyolite and ophiolite in shades of red and purple: a Verrucano rock formed during the Permian–Triassic period. This slightly rounded prismatic boulder covers an area of 743 m² and weighs approximately 2,000 tonnes.
The site of the Pierre de Peyre Ossel was listed by the decree of 9 May 1914:“Erratic boulders, of great interest both for their origin and their location on the edges of high moraines near Gap, are threatened with destruction as a result of the construction of a railway line from La Mure to Gap. The most interesting of all and the most threatened, as it lies barely 200 m from the site of a planned viaduct with a span of 130 m, is situated 3 km from Gap, on the great Bumats moraine and on the right bank of the Buzon torrent. It is a magnificent, slightly rounded prismatic block of quartzite, originating from the Tête de Gaulent, a mountain situated on the border between the districts of Embrun and Briançon”(Extract from a note by the Prefect of the Hautes-Alpes in 1911, addressed to the Under-Secretary of State for Fine Arts).
The archives also mention negotiations with the owner regarding compensation linked to the listing:“the owner of this natural monument, having been approached, is demanding 300 francs to consent to its listing, claiming that the railway contractors would pay him much more.”(Note from the Prefect in 1911).
As the site is listed, it remains open to the public. However, as it is situated on private property and vehicle access is prohibited, it is recommended that visitors walk there and respect the site: do not leave any litter, do not light fires and avoid causing any damage.

The Buzon Viaduct is a civil engineering structure built between 1913 and 1929. It was intended to allow the railway line from Gap to La Mure (the “Champsaur line”, then under construction) to cross the Buzon ravine; however, the line was never put into service. This masonry viaduct, approximately 100 m long, features five semicircular arches, each with a span of 15 m. Its deck, straight and horizontal, is flanked by narrow footpaths and parapets: metal in the centre and masonry at the ends.
Abandoned for decades and even partially dynamited—needlessly—during the Second World War, the structure has nevertheless stood the test of time. Since the 1950s, it has supported the main water supply pipeline for the town of Gap. On the left bank, the absence of embankments led to the construction of a concrete footbridge approximately 20 m long, extending from the abutment. However, a landslide caused significant rockfall at this abutment, leading to the closure of the viaduct to the public in 2013. Following major consolidation and restoration work, the viaduct was incorporated into the V64 cycle route (Grenoble – Gap – Marseille). It reopened to the public at the end of 2025.

The Buzon torrent, a small, deeply incised tributary of the Luye, flows down from the Bayard plateau and is joined by the Oursatas torrent.
These torrents, which are a constant feature in the second half of the route, bring a refreshing touch and a forest atmosphere to the route.