Las Médulas

Las Médulas is a historic gold-mining site. that was the most important gold mine, as well as the largest open-pit gold mine in the entire Roman Empire.

The spectacular landscape of Las Médulas resulted from the "ruina montium" (wrecking of the mountains), a Roman mining technique described by Pliny the Elder. The technique employed was a type of hydraulic mining which involved undermining a mountain with large quantities of water. In order to bring the required quantities of water from the Sierra de la Cabrera, a canal system over 100 kilometres long was built. Parts of this system are still preserved today. Large-scale production did not begin until the second half of the 1st century AD.

Pliny the Elder, who was a procurator in the region in 74 AD, described the technique of hydraulic mining:

"What happens is far beyond the work of giants. The mountains are bored with corridors and galleries made by lamplight with a duration that is used to measure the shifts. For months, the miners cannot see the sunlight and many of them die inside the tunnels. This type of mine has been given the name of ruina montium. The cracks made in the entrails of the stone are so dangerous that it would be easier to find purpurine or pearls at the bottom of the sea than make scars in the rock. How dangerous we have made the Earth!"

Opencast methods would be pursued by fire-setting, which involved building fires against the rock and quenching with water. The weakened rock could then be attacked mechanically and the debris swept away by waves of water.

Pliny also stated that 20,000 Roman pounds (6,560 kg) of gold were extracted each year. The exploitation, involving 60,000 workers, brought 5,000,000 Roman pounds (1,640,000 kg) in 250 years.