The main river running through the Valdejero Park, the Purón rises to the north of Lahoz and flows southwest in a gorge punctuated by caves until it gets beyond the dammed cliffs around Valderejo. Thus it flows through soft pastures bordered by woodland, before encountering more Mediterranean vegetation. Visitors on foot pass by Ribera, of which only a ruined church remains (although its Gothic frescoes may still be seen).