Ecrins trekking

The Arsine Lakes

6 h
Return trip
Return trip
18.1 km
Total Length
1060 m
  • By walk
  • Geology
  • Lake and glacier
  • Pass

Departure : Le Casset (Le Mônetier-les-Bains)

The hamlet of Casset lives according to the changing colours, from the green prairies in the valley to the light blue of the Arsine glacial lakes.

It is hard to imagine that just 60 years ago, the Arsine lakes did not exist and the entire site was covered by ice. Over time, plant life has colonised the new environment: purple saxifrage, creeping avens, campanula cenisia, genepi. There is even life in the cold water of the lakes.

From the car park at the entrance of Casset, near the Park information centre, head up the hamlet by the main street and cross the second bridge over the Guisane, on the left. A straight track follows the Petit Tabuc stream and leads progressively from the hayfields into the woods. Beyond the barrier and the Clot du Gué bridge, a steady climb leads through the larch forest up to Grand Pré glade (1683 m), then on to the Douche lake (1901 m). The heart of the Ecrins National Park starts on the other side of the ford made of wood and stones. A winding footpath over a large area of scree gives well-deserved access to a mineral valley, populated with chamois. In the distance, on the right, the shepherd's mountain hut reminds us that the area is used for grazing. The footpath continues on the right of the valley and ends at the Arsine pass (2340 m). This is where you will leave the GR 54 to go over the frontal moraine of the Arsine glacier. From this ledge created by the movement of the glaciers, two large lakes mark the end of the route (2455 m). The Arsine glacial cirque is overlooked by majestic summits: you will marvel at Les Agneaux and the Neige Cordier Peak. Return by the same route.


Le Casset 17 km from Briançon by the D1091 and D300.

Information desks

Information center "le Casset" (summer only)

At the entrance of the hamlet of "le Casset" and near the core zone of the Park, a stop before or after your walk... Projections, documentation, books of the Park. Free admission. All animations of the Park are free unless otherwise stated.

Le Casset
05220 Le Monêtier-les-bains

Website - Email - 04 92 24 53 27

Lat: 44.98543, Lng: 6.48432

This trek is within park center, please read access rules.

Clic for map interaction

On the way...
Whiskered bat

The whiskered bat is a dark-faced bat. It is quite common in certain mountain regions and is one of the most frequent species after it cousin the common pipistrelle. It likes trees, be they on the banks of a river or in the high altitude forests, but it is also possible to catch sight of them in gardens and villages such as the hamlet of Casset. This small mammal lives on flying insects and thus helps in controlling their numbers. Like all mammals, the female feeds her sole offspring with her milk.  

Lover of old stones

The rock sparrow is a sedentary bird. It generally settles in well-exposed, agricultural areas where there are lots of stones, stone terraces, ruins, piles of stones, old buildings. This southern sparrow can be found up to an altitude of 2000 m provided there is an open landscape and many mineral elements. It nests in the hole of a rock, in a wall and sometimes under the roof of a house. It will then mingle with the house sparrow. A sociable bird, it lives in small, dispersed colonies.

Golden eagle, the Ecrins' mascot

The Petit Tabuc site is ideal for the golden eagle to nest. The golden eagle is amongst the protected species that are considered rare in Europe.  The size of the populations that have been registered in the Ecrins massif, bestow a strong responsibility on the Park for conservation of the species. Counting takes place regularly since 1985 along with monitoring of reproduction, causes of disturbance and mortality.

Ring ouzel

In the pastures covered with larch or 'bush", a cry of alarm followed the start of a song resounds. A blackbird? Yes, but more specifically a ring ouzel. This shy, swift mountain blackbird lives on the fringe of the larch, scots pine, spruce or Swiss pine forests between 1000 and 2500 m in altitude. The ring ouzel is a migratory bird that spends winter in Spain or North Africa before coming back to the mountains around March.

Water colour in the meanders

The turquoise colour of the water that meanders from the Petit Tabuc stream gives a special character to this remarkable site. The valley is popular among photographers and artists for its photographic and pictorial quality.  

Butterflies and moths

Butterflies can be distinguished from moths by the shape of their antennae. You will also notice that when resting, the butterflies wings are vertically folded over the body for necessary discretion while the moth's cover them. The moorland clouded yellow butterfly has another unusual habit: as soon as it becomes too cold to fly, it settles and bends its side to the sun to absorb energy. It can even lean slightly, whereas others tend to fully, and dangerously spread themselves out.

Aquatic diet

The grey wagtail is "hyperactive" and has a diet of flies, mosquitoes, dragonflies and all sorts of aquatic insect larvae. It hunts at the edge of the water, by jumping from stone to stone or hovers to catch its prey. It sometimes fishes for shellfish, molluscs, or even small fish to complete it meals. It does not leave the damp banks to build its nest either, and even looks for somewhere close to a waterfall or to flowing river.


The site of Arsine offers a complex moraine environment with a parade of ice margin flowers. The frontal moraine of the Arsine glacier is on a glacial vegetated rock complex that occupies about forty hectares at the bottom of the cirque. This complex is likely to have come about through a shifting of abandoned glacial deposits after permafrost was established. This means that the ground maintains a temperature of 0°C or less over several years. This phenomenon is likely to have taken place during the recent Dryas climatic cooling, that is to say 11 000 – 10 000 years BC.


This bird is like a tightrope walker suspended in the sky, sounding out a long chorus of notes. Then, triangular wings back, and in a perfect spiral, the bird lands in the middle of the prairie. On the ground, it is difficult to see: its varying shades of brown means it is very well camouflaged. In its search for food, its movements, which are a succession of small sprints and sudden halts, enable it to spot possible predators.

Arsine pass

The Arsine pass, is an important crossing point to visit on the GR54 Tour des Ecrins et de l'Oisans. It gives a remarkable viewpoint over the Angeaux massif. The pass is part of an old itinerary that was used instead of the crossing point by the Lautaret pass. It is also a crossing point between the Guisane and the Romanche area. This is an area that was mentioned as early as the Middle Ages as a place of conflict between the districts of Villar d'Arène and Monétier-les-Bains.

En descendant du col d'Arsine, sous les chalets du même nom. Vue plein est.

Altitude profile

Altitude (m)

Min : 1510 m - Max : 2458 m

Distance (m)