Foothills of the Teleno above the Duerna Nature · Castrillo de la Valduerna, La Bañeza, León Image of Castrillo de la Valduerna, not of the place itself. The district drops from the last south-eastern slopes of the Teleno down to the Duerna flood plain, a stretch of river dotted with archaeological remains and with old water works linked to gold mining. Photo: Rodelar (CC BY-SA 4.0) What to see and do in Castrillo de la Valduerna