Usaide

Its entrance is wide, oval and of large dimensions, covered with grass, and it leads into a large chamber that has been used as a livestock shelter; remains of constructions can be seen. It continues along a wide gallery between large fallen blocks and several changes of direction, with a great quantity of stones covering the floor of the almost horizontal gallery. It has a route of about 200 m. In general it is a cavity of large dimensions, in which there are at least three parts: the upper zone is inactive, with altered rock and collapses of large blocks, and the lower zone is the active one.

A small chamber has concretions. At the bottom of the pit there are speleothems and clay deposits, and the upper gallery has speleothems. The lower zone is the active one, with constructive processes of speleothems and clay deposits.

On the left we find a fissure that gives access to a descending gallery with clay, which connects to a small depression with water and further on to another of larger dimensions, which we cannot pass because it has quite a lot of water. This zone is the deepest part of the cavity (-85 m).

One continues along a wide gallery between large fallen blocks and several changes of direction, continuing for about a hundred metres to come upon a small pit, at first with a steep slope about 12 metres long, then continuing vertically for 30 m, following a gallery parallel to the valley with a great process of collapses, reaching a first pit that connects with the lower galleries. We reach a 10 m ramp; there is a platform from which to descend another 20 m. The descent is made over a large flowstone. We return to the base of the pit and on the right we climb a steep slope of 15 m with the help of a rope, reaching an upper gallery that has speleothems and a slippery floor until we reach another pit. This has dimensions of 6x3 m, with a depth of about 50 m. There are rock slabs in unstable equilibrium. Skirting the mouth of the pit, the gallery continues.

There are traces of Ursus Artus and it has been the setting of the Carlist Wars.