The site of Artiga de Lin constitutes the headwaters of the valley of the River of the João, a tributary of the Garonne. The watershed of this valley limits the basin of Éssera, with peaks and crests climbing steep slopes above 2500 meters, culminating in the Malh des Pois (or Forcanada) of 2881 m. The longitudinal profile is characterized by a series of rocky landings and steps with the presence of small ponds in the hollows of the circuses.
The Artiga de Lin Valley is a magnificent example of the Pyrenean valley of the Pyrenees. In this valley we find the most important example of the capture and rise of the Pyrenees: the Karst system of the Uelhs deth Joèu (1410 m). Through it, they are captured and transferred to the Garona basin, the waters that come from the Aneto and Maladeta glaciers should go to the Mediterranean (www.valdaran.com/listing-item/uelhs-deth-joeu /)
The state of conservation of the natural space is excellent, despite the large influx of visitors. Given its high tourist value (hiker), didactic and scientific justify the inclusion of its entire catalog in the geological heritage.
Vegetation and flora
The vegetation at the bottom of the valley is typically Atlantic with leafy beech and centennial fir trees encased with mosses and lichens. Over the 1800 m, typical meadows and terraces of the alpine lands are developed.
The low valley of Era Artiga de Lin, open on the Atlantic slopes, still presents the typical zonation of these mountains, with a typical landscape of the Baish Aran: acidophilic oak barrels of oak and large leaf oak (Quercion pubescenti-petraeae), Beans with joliu and green eel (Fagion-Sylvaticae), forests of deciduous (Fraxino-Carpinion), firs (Goodyero-Abietetum), salzedes subalpines (Salicion pentandrae), etc. Some of these forest formations are the most spongy representatives of the whole of Catalonia. The culminating summits form a characteristic North-South alignment that closes the valley and already corresponds to extensive supraforestral areas of the country of alpine meadows (Festucion supinae). In various plant communities, we must mention the richness of cryptogamic flora, especially for the abundance of muscular epiphytes and the representativeness and diversity of Atlantic fungi species. 
The natural systems of Era Artiga de Lin are characterized by exceptional diversity and faunistic wealth. Much of the Aranese fauna is well represented, as is apparent from the fact that the brown bear (Ursus arctos) is still alive. Certain species such as, for example, the rooster (Tetrao urogallus), live in forests of deciduous trees, something extremely rare in other parts of the Pyrenees. Other forest species of interest are, for example, the Pyrenean owl (Aegolius funereus). In the culminating subalpine areas, slices may also be found (Perdix perdix).
Due to its diversity or singularity, invertebrate fauna is particularly interesting, and in particular, the arthropods that present in this space one of the most diverse areas in the central Pyrenees. Thus, there are several species of heteropter, very rare in the rest of Catalonia and in the Iberian Peninsula, and numerous Pyrenean species of very rare molluscs in our territory (Acicula clupuyii, Chondrina bigorriensis). In this EIN, there are also interesting species of lepidoptera, such as Maculinea arion, Parnassius apollo or Parnassius mnemosyne.