This 33,440 ha area, which represents the best high mountain ecosystems of the Iberian Peninsula, gathers more than 45 peaks over three thousand meters high, as well as 13 glaciers –declared Natural Monuments–, astonishing cirques or lovely high mountain lakes, known as ‘ibones’.

In the highest altitudes, there are black pines and junipers and, just as we go deep into the tree line, we find beeches, firs, birches, hazelnuts and boxes that are home for several fauna spices: nival partridges, Pyrenean tritons, marmots, vipers, mountain goats (sarrios), griffons, vultures, bearded vultures and golden eagles. In the valley areas, there are also squirrels, moles, roe deers and a wide range of birds that prowl at ease.

Inside this vast area, always following the mandatory preservation rules, visitors can practice outdoors activities such as hiking, alpinism, cross-country skiing, snowshoes, ski mountaineering, canyoning, climbing, horse riding or bike touring.

Geomorphology

Posets and Maladeta massifs are two of the highest mountain hubs in the Pyrenees, including the two highest summits of this mountain chain, Aneto (3,404 m) and Posets (3,375 m).

The Quaternary glaciers were the main erosive agents that formed the natural park landscape. Over granite, limestone and slate, this glaciers sculpted long valleys in a ‘U’ shape, colossal cirques and deep basins that nowadays are taken up by hundreds of ‘ibones’, name given to the glacial-origin mountain lakes.

When these lakes silt up due to sedimentary stuffing and vegetable remainders accumulation, the peat bogs (moss-covered and waterlogged terrains with islets, small muddy canals and sandy shores) emerge.

Currently, there are three small-sized glaciers that remain in the massifs of Posets, Perdiguero and Maladeta which have been declared Natural Monuments.

These granitic massifs have high reliefs and sharp crests. However, the scarps induced in the granites by the glacial erosion are not as vertical as in other Pyrenean calcareous massifs. Given this slightly low gradient, we find heavier shapes spattered with lakes and glacial erosion evidences.

The karstic phenomenon is also important in areas such as Forau de Aigualluts chasm, in which the water from Aneto’s glacier disappears and, after flowing underground during 4 km, reappears to nourish the Garona river in the adjacent Arán Valley.

Hydrology

The main water courses of Posets-Maladeta Nature Park are Cinqueta river that drains Chistau Valley (western sector), the headwaters of Ésera river that drains Benasque Valley (central sector) and Noguera Ribagorzana river that drains Barrabés Valley already out of the nature park (east sector).

Apart from the main courses and due to the hydrologic and geomorphologic value, it is also worth emphasizing several courses and transversal cliffs such as Salenques and Llauset in Noguera Ribagorzana, Ballibierna, Estós and Eriste branches of Ésera river, and Cinqueta de la Pez and Cinqueta de Añes Cruces cliffs that join together to give rise to Cinqueta river.

Likewise, there are many lakes (ibones). The ice masses in the cirques and in the glacial troughs give rise to over-excavations where the water is collected after the ice melting. In the nature park territory, there are approximately one hundred glacier-originated lakes that, depending on their altitude, can remain frozen for more than 6 month a year. Some of them are: Bachimala, Millares, El Sen, Barbarisa, Perramó, Batisielles, Coronas, Llosás, Ballibierna, Cregüeña, etc. The wáter from other lakes such as Billamuerta, Paderna or Escarpinosa is shallow and greenish, almost marshy due to the sediments filling, and they are surrounded by vegetation consisting in rushes, sphagnum and black pine sedges.

The river flow regime in this territory is characterized by high flow rates from spring months to early summer as a result of the melting and the spring rains; and by low flow rates during winter and early spring due to the limited rainfalls.

Flora y fauna

Around this area, there is a large flora and fauna diversity due to the great elevations and the topographic and lithologic heterogeneity. From the highest glacier and tundra environments, the following vegetation sequence takes place: alpine and subalpine pastures, fir forests, mesohydrophylic mixed forests, wild pine forest and oak forest mixed with boxwoods. There are also interesting botanical settlements including casmophitic and scree terrains.

In the peat lands, the most common flora is the cotton grass (Eriophorm agustifolium and E. Latifolium) and the carnivorous plants such as the large-flowered butter-wort (Pinguicula Grandiflora) or the roundleaf sundew (Drosera Rotundifolia) that, in order to supply the lack of nitrogen or phosphate, they feed on insects.

In the nival ground, there are birds such as the white-winged snow finch, the alpine chough and other perching birds, and during summer days one of the most characteristic animals is the ‘sarrio’ or Pyrenean mountain goat (Rupicapra pyrenaica). In the lower snowdrift areas, there is a trophic net that starts with cryoplankton, fungus, algae, moss and bacteria, and continues with nematodes, mites and tardigrades, finishing with carnivorous insects and perching birds that visit the snowdrifts to eat.

In alpine and subalpine pastures, over 2,000 m high, there are rock ptarmigans (Lagopus mutus), marmots and ermines (Mustela erminea).

In rocky areas and ledges, the species to underscore are the sarrio, the golden eagle (Aquila chrysaltos), the bearded vulture (Gypaetus barbatus), the alpine chough (Pyrrhocorax graculus), the wallcreeper (Tichodroma muraria), the white-winged snowfinch (Montifringilla nivalis), the Pyrenean rock lizard (Lacerta bonnali), etc.

The fauna in the mountain wetlands (rivers, streams, lakes, springs, peat lands and other puddly areas) consists of endemic species that include the Pyrenean desman (Galemys pyrenaicus) and the Pyrenean mountain newt (Euproctus asper). In peat lands, the most characteristic is the viviparous lizard (Lacerta vivipara). Also linked to water courses, we find the otter (Lutra lutra).

Several species seek refuge in the nature park forests: boreal owl (Aegolius funereus) or western capercaillie (Tetrao urogallus), as well as wild boards, squirrels, foxes, etc.

In order to protect these valuable settlements, remember: 

Do not leave the marked tracks, thus you will not disturb the fauna and you will have a better perception of the landscapes.

The access to certain forest tracks is regulated, bear in mind the signposting.

Walking in silence will bring you the opportunity to observe the fauna and you will have a better perception of the landscapes.

Neither harm nor pull out the flora.

After your visit, pick up the rubbish and place it in a bin.

You now know well how important water is, do not spill rubbish or use soaps in streams, rivers or other water courses.

Camping inside the nature park is only allowed in high mountain modality, meaning over 2,000 meters high, from 20:00 to 08:00 h, and at more than 500 meters from a refuge.

Fire is not allowed. If you see smoke or other irregularities, please call 112 (SOS Aragón). The call is free and they will deal with any emergency.

Summer storms and sudden temperature falls are common. It is advisable to always carry warm clothes. Please, find out about the weather forecast before planning your activity.

Nature protection agents and staff from the Interpretation Centres will remain at your disposal for any doubt or suggestion at any time.

Forau d'Aigualluts visit

Visiting Aigualluts is a perfect plan to enjoy one of the most relevant karstic phenomenons of the Pyrenees. A thunderous crystalline waterfall falls in an enormous drain enclosed in an idyllic setting surrounded by bucolic meadows.

As if it were a spell, the water from the impressive drain or ‘forau’ de Aigualluts disappears, reappearing again some kilometres away in Arán Valley; an easily accessible natural spectacle of unique beauty that occurs under Aneto’s gaze and the perpetual glacier.