Las Médulas Monument · Carucedo, El Bierzo, León The largest open-cast gold working of the Roman Empire, excavated by the ruina montium technique between the 1st and 3rd centuries. Its reddish clay pinnacles and its galleries were inscribed by UNESCO on the World Heritage list in 1997. Photo: Anual (CC BY-SA 4.0) What to see and do in Carucedo