This extensive 20km cave system, exploited as a lead and zinc mine before 1979, makes for a popular outing inland from San Vicente. The one-hour visit goes 400m into the cave in a mine train, then continues on foot. Booking ahead is highly recommended. For thrill-seekers, the ‘adventure’ tour (€32, 2½ hours) travels 3km into the cave, opening up an extraordinary subterranean world. It’s 30km southwest of San Vicente: turn east off the CA181 at Rábago and continue 7km uphill.