Sistema Añelarra

The Larra massif is one of the most impressive areas of karst morphology shaped by limestone dissolution processes in Europe and dates from the Quaternary Era, when there was a significant ice cap, with a tongue that extended for about eight kilometres. The system results from the union of 3 cavities: Pozo Estella (AN.3), Pozo de Frontenac (AN.6) and Pozo de los Dos Acuarios (AN.51). These cavities consist entirely of significant continuous verticals in limestone rock, which makes them technically difficult and physically demanding.

At the bottom of the cavities one reaches the junction with the river, where there are fairly wide areas with large chaos of rock blocks formed basically of basal sandstones.

The descent through the cavities consists entirely of significant continuous verticals in limestone rock, which makes them technically difficult and physically demanding, until reaching at their bottom the junction with the river.

The Larra karst massif has been considered one of the main areas in the world with high speleological interest, from where the Diputación Foral de Navarra has promoted scientific expeditions from a geological, hydrological, geomorphological, tectonic, biological, etc. interest, as well as from a sporting point of view. Exploration work continues today with promising results, where in a not very distant period of time extraordinary levels of development will be achieved in the system.