Deboyo Cave Nature · Caso, Nalón, Asturias Deboyo cave, located in the biosphere reserve of Redes Natural Park, in the council of Caso, is a 200-metre karst cavity through which the Nalón river flows, near the village of Les Yanes, in the parish of Campo de Caso, parallel to the AS-117 road. It shelters the roosts of five bat species found in the park: the Mediterranean horseshoe bat, the river bat, the greater horseshoe bat, the dwarf bat and the cave bat. It was declared a natural monument of Asturias on 22 May 2003. Photo: Groserus (CC BY-SA 3.0 es) What to see and do in Caso