These are old copper and sulphur mines 3km north of Nerva (6km east of Minas de Riotinto). Here you see the source of the Río Tinto and a 65m-deep opencast mine, and are taken into a 200m-long underground mine gallery. There are three guaranteed daily visits but schedules vary, so it's essential to book ahead through the Museo Minero (by phone or online).
