Underground slate mine of Odollo Curiosity · Castrillo de Cabrera, La Cabrera, León Image of Castrillo de Cabrera, not of the place itself. Odollo is home to the only underground slate working in La Cabrera: while the rest of the comarca's quarries work open-cast, leaving grey spoil heaps on the hillside, here it is extracted in galleries beneath the mountain. Photo: Rodelar (CC BY-SA 4.0) What to see and do in Castrillo de Cabrera