Updated 18th January 2004; 12th October 2016; 20th January, 5th February 2017
The cave entrance, in the north bank of the Asón, is best approached by swimming across from south bank - at least that is what an explorer from the 1978 Matienzo expedition suggested. "Landing is on mud and a squeeze on the left enters a rift which leads to a second, higher entrance." There is a sketch from the first documented exploration in the 1978 logbook. The table in anon., 1993a has the cave at 60m long but the survey shows rather less passage.
The cave entrances are to the southwest of the cemetery in Ogarrio. A 200m walk from the road following a wall at the edge of a grassy field leads to a slope down to the right towards the river and short path to the top entrance beneath trees.
The walking-size rift has been pushed in a hole up on the right hand wall since its exploration in 1978. The surveys don't show the passage down to the river entrance but there are indications in the floor of a route down, currently choked with boulders.
Water from the river Asón sinking in or near the cave resurges at Fuente Isena, 5km away near Ramales. During extreme droughts these sinks have taken all the river, so that the local people blocked them, after which the Fuente Isena dried up.
A more comprehensive and up-to-date description (in French) by Guy Simonnot is found here.
References: Mugnier C, 1969;
anon., 1978 (logbook) (sketch); Corrin J S and Smith P, 1981; anon., 1993a (survey); anon., 2017a (January, February logbook)
Entrance pictures : January 2017
Underground pictures: January 2017
Sketch survey: from anon., 1978 (logbook)
Detailed Survey : from anon., 1993a (AEC Lobetum): high res low res
from Guy Simonnot (2016) - plan : section : 3d jpg
Line Survey :
On area survey :
Survex file :