Ayeres' big loop
Summer hike
Ayeres' big loop

Ayeres' big loop

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An easy hike between mountain forest and alpine meadows, with the mont Blanc in perspective
It is first of all an immersion in the forest with its charming green colored Lac Vert. Then, as you go higher up, you’ll come across mountain pasture hamlets, traces of former pastoral life. After that you’ll follow a horizontal trail with view on the Mont-Blanc and finally plunge back into the forest on a wide track.

23 points of interest

  • Fauna

    The placid Ibex

    The Ibex is not very shy, especially compared to the Chamois sharing its territory.
    Unlike most other mountain species, it remains at altitude even when winter and snow arrive.
    It then reaches ridges and snow-cleared areas where it will more easily find grass to feed on. This search for food costs a lot of energy. So, if you see it, do not approach and let it leave quietly in order to avoid wasting its precious energy, especially in winter.
  • La Maison de la Réserve

    The exhibition an information office Maison de la Réserve naturelle de Passy is located in Plaine-Joux and welcomes you during the school holidays. The permanent exhibition about fauna, flora and landscapes will open the doors to the nature reserve. You may find answers to some of your questions here and can admire the wild species hidden in nature. If the Maison de la Réserve naturelle is closed, don’t worry, go up to the passageway. There is permanent free access to information about former (geological times) and present landscapes, the wonders of biodiversity and the great challenges of the mountains of the future (water, glaciers, global warming...).
  • Fauna

    Golden Eagle cainism

    In their nest perched against a rock wall, two chicks will soon emerge from their eggs. Only one will survive: the weakest one will be killed by the strongest! In biology, this behavior is called "cainism".
    This phenomenon is common for diurnal raptors, since it is part of the species survival strategy: selecting straight away the strongest in order to increase its chances of reaching adulthood. For the parents, it's indeed a great job to feed a voracious juvenile which, from 100g at birth, must reach 5kg by the time it starts flying!
  • Geology

    The mont Blanc

    Beneath the snow and the glaciers, two main rock types form the Mont-Blanc Massif: the sharp edges and the highest peaks are made of very hard granite (from the left to the right: Aiguilles de Chamonix including Aiguille du Midi, Mont Blanc du Tacul, Mont Maudit, summit of mont Blanc) while the rounder - because softer - parts are in gneiss (from the left to the right: Dôme du Goûter, Aiguille du Goûter, Aiguille de Bionnassay,...).

    These two so-called crystalline rocks come from the core of the Earth in fusion.
  • The history of Plaine-Joux

    From forest to mountain pasture, Plaine-Joux has not always been a ski resort as reflected in its name, which would mean "forest on a flat space".

    As early as the 1930’s, the inhabitants of Passy were already practicing ski activities in this location enjoying a magnificent panorama. It was around 1965 that it officially became a communal ski resort. Even nowadays, Plaine-Joux remains, as well in summer as in winter, a popular family resort for skiing, hiking, paragliding... and contemplation.
  • Fauna

    The Common Minnow and the Common Chub

    Minnows are very common in highly oxygenated waters. Its presence in high altitude lakes is due to trout fishing activities. Used as bait by fishermen, it colonized these mountain lakes.

    The Chub is a rather large fish, very widespread in France. It is an omnivore, which means that it eats everything. In many European countries, especially in the east, it is of highly culinary interest.
  • Fauna

    The common Toad

    Kissing a toad transforming it into a charming prince is a myth! You must not touch this protected species, which is sensitive to diseases that humans could transmit.
    But you can look it in the eyes to observe its horizontal pupil and its orange iris. You will also notice its parotid glands on the back of its head. They are used to secrete a venom, the "bufotoxin" intended to keep away any possible predator.
    The toads and frogs are not the same species; toads live mostly in the forest, out of the water, joining it only during the breeding season !
  • Fauna

    The Grass Snake

    Semi-aquatic, it mainly frequents wetlands but also drier environments hosting its main prey, such as amphibians (frogs, toads, salamanders or newts).
    It's a protected species, like all reptiles!
    It can be identified by its round pupils, its olive grey color and its double black and white or yellow collar shaped pattern. Or by another special feature: when it feels in danger, it spits out a foul smelling liquid and pretends to be dead, revealing its two-colored piano pattern on its ventral surface!
  • Fauna


    Odonates, more commonly known as dragonflies, are insects.
    There are two stages in their lifecycle: a "larva" (or nymph) stage which is aquatic followed by a terrestrial stage, when the adults are grown to adults.
    Dragonflies are predators: they are carnivores that feed on different types of prey depending on their stage. They eat other insects as well.
    Their distribution is strongly linked to climate conditions and any change has a strong impact on their presence. Destruction of their wetland habitats is one of the main threats to dragonflies.
  • The alpine cabin

    The alpine cabine is a small building which, gattered with others, forms a small hamlet. These constructions were originally intended for the organization of agricultural life in the mountains. These cabins were used in the summer to shelter the shepherds and their family. They were also used for milking and the production of cheese and other dairy products.
  • The history of the Passy nature reserve

    During the 1970s, the wealth of the natural areas of Haute-Savoie were highly conveted. The appetite of promoters and the many tourist development projects raised increased protest. The French State responded by the creation of 9 national nature reserves.

    The national nature reserve of Aiguilles Rouges was created in 1974, and a few years later in 1977 the Sixt-Fer à Cheval / Passy nature reserve.

    A small territory, settled between these two areas, will become the nature reserve of Passy in 1980.
  • Architecture of mountain pasture chalets

    Some of the alpine cabins are more than a century old.

    Construction features at high altitude are strongly related to the immediate surroundings: stones for the walls, basic – but resistant to winter conditions! – framework made out of spruce.

    Originally, the roof was covered with ‘tavaillons’, a kind of wooden tiles.

    These buildings, used for agricultural activity during the summer, were of rudimentary comfort and housed the shepherd and its owner’s family.
  • The 'Ayères'

    Originally, the word "Ahier" comes from a roman patois meaning Sycamore Maple. The words "pierrières" and "roc" are references to the numerous boulders, evidence of the landslides of Dérochoir, including the one in 1751 which killed 6 people and a few domestic animals. All these cabins were alpine cabins for agricultural use. They are now used as holiday cottages.
  • Flora

    The Downy Birch

    There are four species of birch in Europe and the one growing here is the Downy Birch. Its sap and bark have many medicinal properties, and is useful for natural drainage and as a remedy against rheumatism, fatigue or allergies!
    In the reserve, birches are monitored as part of the "Phénoclim" program implemented by CREA and intended to measure the impact of climate change on plant cycles.
  • Flora

    The Mountain Ash

    It is a small tree growing in forest edges. Its fruits are red orange berries loved by thrushes and blackbirds.
    The fruits can be used to make to make brandy, jelly or jam. But be aware that they are toxic at maturity, so you have to pick them earlier!
    In the nature reserve, the Mountain Ash is part of a participatory science program intended to measure the impact of climate change on the ecosystems of the mountain.
  • Fauna

    The whistled language of groundhogs

    Groundhog is the favorite meal of the Golden Eagle and an important item in a fox diet.
    Always vigilant, standing up, it surveys its environment to avoid to be caught. Thanks to a very wide field of vision, and excellent hearing and smell abilities, nothing goes unnoticed. In case of alert, it warns the others with an alarm call: very high-pitched and brief for a danger coming from the sky, whistled and repeated for a danger on the ground. And that danger may be you!
  • Fauna

    The Hazel Grouse

    It is the smallest and most discreet of the mountain Galliformes species.
    It is much less known than the Black Grouse or the Rock Ptarmigan because it lives exclusively in the forest!
    But it is as important as the others from a biological and scientific point of view: it is an indicator species of environmental changes. Its specific demands in terms of vegetation and diversity of tree species ask for an adapted forest management. Bad preservation management of this habitats is one of the main causes of regression of the species.
  • Fauna

    The Black Woodpecker

    It is the largest of the 8 woodpeckers present in France. Originally an exclusive mountain species, it is now also found in the valleys! Indeed, it adapts to both deciduous and coniferous forests, as long as they cover large areas and include dead wood and old trees with large diameters.
    It is easily recognized by its entirely black plumage enlivened by a bright red spot, limited to the nape on the females and more extensive on the males.
  • Fauna

    The Golden Eagle

    Everything about this bird is exceptional! With a wingspan up to 2 meters, each couple controls a territory as big as 10 000 football pitches! Its X-ray eyes detect prey movements for over 1 kilometer of distance. Its eyes are like magnifying glasses that magnify 6 to 8 times what its perceives and it has a 240 degrees field of vision. In addition to colors, it is able to detect ultraviolet light, a major asset for this great hunter who can swoop down on its prey at a speed of 350 km/h. But no one is perfect: it misses 9 prey out of 10!
  • Fauna

    The Common Raven

    It is the largest of all passerines and corvids!
    Alternately feared or venerated, it is the hero of myths and legends in many cultures. Persecuted for a long time, it is now protected. The size of a buzzard, it can be specifically recognized by its diamond-shaped tail and its hoarse call. It is an omnivore, which means that it feeds on carrion, eggs, chicks or berries!
    The couples, which are united for their life time, carry out aerobatic courtship rituals! Apart from humans, the Golden Eagle is its only predator.
  • Fauna

    The Griffon Vulture

    It visits the Haute-Savoie region during the summer. The species is monogamous, that is to say that couples stay together for their entire life!

    This bird lives in colonies of different sizes, the closest of which are located in southern Vercors. Especially the young individuals who explore new territories. To feed, this bird is also able to cover hundreds of kilometers thanks to its gliding technique, depending on favorable weather conditions.
  • Peak

    The mont Blanc before mountaineering

    Many mountaineers dream of climbing mont Blanc, the highest peak in Western Europe. But it has not always been that popular. In the past, the inhabitants of mountain villages were scared of the mountains environment which led to numerous superstitions, as you can tell from the names given to the summits (“Mont Maudit”, meaning Damned mountain, Aiguilles du Diable, meaning Devil peaks, etc.). Only shepherds, chamois hunters and crystal miners (mining rock crystals) frequented these hostile environments. The first ascents were made by daring "outsiders" who employed these mountain experts as guides.
  • View on Le Dérochoir

    Le Dérochoir is the result of successive landslides. The first known and documented dates back to 1471. The second and last, at least for the moment, occurred in 1751. At the foot of the cliff stands a huge landslide cone which forms an unstable slope.
    These various landslides created a passage making it possible to cross the Fiz ridge.


Departure from Maison de la Réserve naturelle de Passy.
  1. Take the paved road to Lac Vert.
  2. Take the track on the right between the treehouses.
  3. Follow the direction Lac Vert.
  4. Take the paved road to the right to Lac Vert. Beacon 93.
  5. Take the track to the Châtelet d'Ayères refuge. Beacon 159
  6. Stay on the track to the Châtelet d'Ayères refuge.
  7. Take the track on the right to the Châtelet d'Ayères refuge. Beacon 95.
  8. Pass the refuge and head to Col et Lac d'Anterne, Lac de Pormenaz. Beacon 161.
  9. Stay on the track to Col et Lac d'Anterne, Lac de Pormenaz. Beacon 162.
  10. Stay on the track to the Chalets du Souay, Lac de Pormenaz.
  11. At the Souay chalets, stay on the track to Châlets des Ayères des Pierrières. Beacon 97.
  12. Take the direction of Châlets des Ayères des Pierrières, Plaine-Joux. Tag 121.
  13. Cross the hamlet of Châlets des Ayères des Pierrières.
  14. Stay on the track to Plaine-Joux. Beacon 17.
  15. Stay on the track straight ahead to Plaine-Joux. Beacon 16.
  16. Stay on the track straight ahead to Plaine-Joux.
  17. Stay on the track straight ahead to Plaine-Joux. Beacon 103.
  18. Head to Maison de la Réserve Naturelle. Beacon 102.
  • Departure : Maison de la Réserve naturelle de Passy
  • Arrival : Maison de la Réserve naturelle de Passy
  • Towns crossed : Passy

Altimetric profile

Sensitive areas

Along your trek, you will go through sensitive areas related to the presence of a specific species or environment. In these areas, an appropriate behaviour allows to contribute to their preservation. For detailed information, specific forms are accessible for each area.
What do you want to do ?
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Impacted practices:
Aerial, , Land, Vertical
Sensitivity periods:
Asters - Conservatoire d'espaces naturels de Haute Savoie
Christelle BAKHACHE : 06 49 99 99 48


Always be careful and plan ahead when hiking. Asters, CEN 74 can not be held responsible for the occurrence of an accident or any inconvenience on this itinerary.


Bus SAT Mont-Blanc L85

Access and parking

Access the Passy Plaine-Joux resort by road D43.
Parking at the entrance of the station.
Bus line L85 (SAT Mont-Blanc).

Report a problem or an error

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