Olatz

Called a pit to distinguish it from the cave, it is a sinkhole set in the contact of schistose terrain with the 2nd bar of Urgonian limestone. The crawls in the form of flat-out passages and meanders advance in favour of the dip of the strata, which are 35ºSW, taking the schists as their base. The 3x2 entrance has a 2m step and gives access to a wide gallery. To the left, it narrows between the bedding planes, forming a flat-out passage. After 50m there is a meander that leads to a wide chamber. After this chamber the meander cuts down between rock and flowstone, but soon widens and runs along a wide gallery of 14m. Then the gallery undergoes a strong inclination and takes the form of a flat-out passage for 18m, where it turns 75º and continues as a flat-out passage, this time horizontal, following the dip of the strata for 30m. From this point the watercourse is confined in a narrow meander, at times occupying 60% of it. At survey point "0" the water occupies almost the whole of the meander, besides being very narrow (0.50m).

The wide chamber presents an abundance of chemical-lithogenic deposits. In its upper part it has fossil meanders much earlier than the active one at its floor.

It is an active and passable sinkhole where the waters of a surface stream that penetrates between bedding planes end up. The floor of the flat-out passage situated to the left is traversed by a stream of 1l/sg. In the centre of the chamber runs a meander with a current of water, which is increased by a contribution it receives at the end of it.

Progression is very uncomfortable and narrow. At survey point "0" the water occupies almost the whole of the meander, besides being very narrow (0.50m), which makes exploration impossible.