Las Médulas was an ancient Roman gold exploration in the open and is today a grand and spectacular landscape of reddish formations and chestnut and oak groves, on the site formerly occupied by Mount Medilianum. Using a rudimentary excavation process known as the ruin montium, the Romans dug small wells and galleries on ancient Mount Medilianum, where they led the course of straying rivers. The force of the waters eroded the crumbling cliffs that allowed the washing of the sediments, revealing the precious metal sought. This activity shaped the natural landscape, giving it a unique and unmistakable look.
That's interesting. I didn't know the Romans operated these sorts of mines. I live in a part of California near where a similar method was used to extract gold from the Sierra Nevada foothills. The miners directed rivers into aquaducts and pipes, and then through giant water cannons that directed huge flows onto the hills, washing them into the mine works for the extraction. This produced so much sediment that it has only in the last few years finally all washed out of the San Francisco Bay into the Pacific. If you drive along the main highway between San Francisco and Reno (Interstate 80) you will at one point drive through one of these areas. The red cliffs are similar to these and are unmistakable.
Gorgeous photo.