Las Médulas (As Médulas or As Meduas in Galician language) is a historical site near the town of Ponferrada, Spain. It used to be the most important gold mine in the Roman Empire. In order to remove the gold, the Romans washed away an entire mountain. From the 2nd to the 4th century AD the Romans used slaves to mine about 900 tons of gold. It left a series of rock pinnacles, gullies, caves and tunnels. Las Médulas is listed by the UNESCO as one of the World Heritage Sites.