This is what is left of a mountain massif in Spain after the method Ruina Montium was used by the Romans. With the help of slaves, tunnels were dug in the mountain, through which the water was then diverted by at least seven aqueducts.
The water literally broke the mountain into pieces and then helped to wash out the gold. It was probably the most important mine of this ore in the entire Empire. We know about this mining method used by the Romans thanks to Pliny the Elder, who held the office of administrator in Spain.