These caves are part of the karstic complex of "Ojo Guareña", which has been recognised as a Natural Monument according to the "Ley de Espacios Naturales" (Law of Natural Spaces), due to its complex network of subterranean galleries, and also declared "Bien de Interés Cultural" (Asset of Cultural Interest). This complex constitutes the largest network of chasms, subterranean rivers and galleries in Spain and one of the most important in Europe.
There are numerous samples of interesting cave-dwelling fauna to be found inside the cave, as well as invertebrate species that are unique in the world. The karstic complex is one of the biggest in Europe and, with over 100 kilometres of subterranean galleries, it constitutes an interesting archaeological site of the Mid Palaeolithic era. Though it has 18 principal entrances, currently, the only public access is via the shrine of San Tirso and San Bernabé, situated in the most emblematic, historic and picturesque part of the zone. See Ojo Guareña on google maps here.
Merindad de Sotoscueva - caves webpage / Plus a list of routes for a walk in the area here.
