Socavón de Purísima is the large chimney of a former mine. To get here from Real, head off down Allende and veer right at its end. Follow this road until you reach the chimney (about 45 minutes one way). The road passes through a cut or split rock, the Cerro Trocado. If open, you can enter the mouth of the mine.
To return, it's a longer and harder slog back up the hill. Be sure to take water, a hat and strong footwear; it's dry and unforgiving country out here.