Cave of los Diablos de Gestalgar Nature · Gestalgar, Los Serranos, Valencia Image of Gestalgar, not of the place itself. Cueva de los Diablos, a natural cavity in Gestalgar formed by water seeping onto the rock, which has given rise to singular formations and may hold fossil remains. It lies at 900 metres above sea level, on the slope of the Peña Roya. In the past, shepherds used it as a shelter for livestock. Photo: Wikipedia / Wikimedia Commons (CC BY-SA) What to see and do in Gestalgar