Updated 5th November 2003; 31st October 2007; 4th, 8th December 2015; 9th February 2016

   A through trip is described from the bottom entrance resurgence, called Cueva de Esquileña (site 4271).

   Optical brightener poured into the stream in the final chamber of the Orillón system was strongly detected at the Esquileña resurgence (November 2015 and January 2016). Detectors at the eastern resurgence (site 4272) in the Mortiro depression that feeds water into the top entrance also tested clearly positive after a repeat test in January 2016. The details of the tests are found here. (Results seen on cotton wool in chicken wire: negative and positive.)

   The survey in Actividades Regionales. Exploraciones en Cantabria (anon., 1993a) is a copy of the reference survey in Report of the British Expedition to Matienzo (Kendal Caving Club and Manchester University Speleological Society, 1975). Valero Enrique y Soriano Ángel, 2007 reports the length as 800m.

Link to entry in the Cave Diving Sump Index.

References: anon., 1974b (logbook); anon., 1974a; anon., 1975b (Easter and summer logbooks); Kendal Caving Club and Manchester University Speleological Society, 1975 (survey); Fernández Gutiérrez J C, 1975; Manchester University Speleological Society, 1982 (survey); Mills L D J, 1981; Corrin J S and Smith P, 1981; anon., 1993a (survey); Valero Enrique y Soriano Ángel, 2007; anon., 2015d (autumn logbook); anon., 2016a (January, February logbook)
Entrance picture : yes
Underground picture(s):
Detailed Survey : hi res   low res
Line Survey :
On area survey :
Survex file : yes (coordinates taken from paper 1975 survey then adjusted for GPS'd entrance positions) : with Coverón (part), CEZ and Orillón