Las Medulas is an historic mining site near the town of Ponferrada in the region of El Bierzo, which used to be the most important gold mine and largest open pit gold mine in the entire Roman Empire. Las Medulas Cultural Landscape is listed by the UNESCO as one of the World Heritage Sites. Advanced aerial surveys conducted in 2014 using LIDAR have confirmed the wide extent of the Roman-era works.
The spectacular landscape of Las Médulas resulted from the ruina montium, a Roman mining technique described by Pliny the Elder in 77 AD. The technique employed was a type of hydraulic mining which involved undermining a mountain with large quantities of water. The water was supplied by interbasin transfer. At least seven long aqueducts tapped the streams of the La Cabrera district at a range of altitudes. The same aqueducts were used to wash the extensive gold deposits.
The area Hispania Tarraconensis had been invaded in 25 BC by the emperor Augustus. Prior to the Roman conquest the indigenous inhabitants obtained gold from alluvial deposits. Large-scale production did not begin until the second half of the 1st century AD.