Grotte di Alta Ribagorça

The Alta Ribagorça contains 18 catalogued cavities, divided into 9 caves and 9 pits. Together they total 602 metres of length and reach a maximum depth of 89 metres. The dominant lithology is limestone, present in 16 cavities, while granite and gypsum are each represented by 1 cavity.

The Forat del Graller, in the Vall de Boí, within the Parc Nacional d'Aigües Tortes i Llac de Sant Maurici, is the longest cavity, at 211 metres, and the deepest, with 89 metres of vertical drop. The Forat del Mont, also in the Vall de Boí, has 60 metres of length and a total vertical drop of 20 metres (-5/+15). Other notable cavities include the Graller del Portús, 40 metres deep in the serra de Sant Gervàs (Pont de Suert), with an entrance of 8x5 metres in a doline, explored since 1966, and the Graller de Sant Roc, with 35 metres of vertical drop in the municipality of Pont de Suert, with an entrance of 8x3 metres and a shaft of 28 metres.

Among the less developed cavities are the Forat d'Irgo, a small pit 24 metres deep in Irgo (el Pont de Suert), with two entrances connected by a small passage between a chaos of blocks, and the Cova de Fesolerets, 39 metres long in Viu de Llevata (el Pont de Suert), known for a long time and published in 1981 by Josep de la Vega.