Iron Mine of Cueva del Hierro Monument · Cueva del Hierro, Serranía Alta, Cuenca Mining works with more than five kilometres of underground galleries, part of which can be visited. Iron extraction goes back to the Celtiberians of the Second Iron Age and was expanded by the Romans, continuing until it ceased in the mid-20th century. Photo: Feliuvilassar (CC BY-SA 3.0) What to see and do in Cueva del Hierro