The Castrón river and its mills Nature · Ferreras de Arriba, La Carballeda, Zamora Image of Ferreras de Arriba, not of the place itself. The Castrón crosses the municipal district among alders and poplars and drove several flour mills that are still standing; its basin was in the front line of the great fires that devastated the sierra in 2022. Photo: JJLORENZO (CC BY-SA 4.0) What to see and do in Ferreras de Arriba