Las Médulas is a natural landscape formed by an old Roman gold mining operation, being considered the largest open-pit gold mine in the entire Roman Empire.
The engineering work carried out for gold extraction involved the modification of the ground conditions, resulting in a landscape of reddish sands, currently partially covered with chestnut and oak trees. It is considered a cultural landscape and it is labelled as “Cultural Park”.
The system used was called Ruina montium. Water from mountain streams was channeled and dammed at the top of the gold exploitation; the mountain was perforated by a network of mining galleries, releasing the water through them. The water pressure dragged the gold lands to the washeries. The hydraulic system of Las Médulas is the most spectacular of all that are known, for the amount of water used, as well as for the length and the large number of branches of its channels.
After being abandoned in the third century, chestnut trees grew where the gold mines used to be. These trees can be seen throughout the route in all its spectacular forms.