Las Médulas

Las Medulas is a historic gold-mining site near Ponferrada in Leon province, Spain, and was the most important and largest open-pit gold mine in the Roman Empire. Beginning in the 1st century AD, Romans used ruina montium, a hydraulic mining technique employing pressurized water channeled through long gravity canals to collapse mountainsides and expose gold deposits. After two centuries of operations, the Romans withdrew, leaving a dramatic landscape of sheer red-rock formations. The site was inscribed as a UNESCO World Heritage Site in 1997.