Scientists have found a 2,000-year-old network of channels and reservoirs in the Eria river valley of Leon, Spain, that would have been used by the Romans to extract gold.
The largest opencast gold mine of the Roman Empire, Las Médulas is also located nearby in León, but until now scientists had no idea that they had also been searching for the precious metal further to the south-east.
The mine, which is hidden beneath heavy vegetation, was discovered by researchers from the University of Salamanca using a Light Detection and Ranging (LiDAR) laser system that was attached to an aircraft.
These lasers were beamed at the ground, and the pattern they reflected back was then measured and compared to geographical information to create a visualisation of hidden features on the Earth’s surface.
The discovery will help us understand more about how the Romans lived and mined back in the 1st century BC, and has been published in the Journal of Archaeological Science.
"The volume of earth exploited is much greater than previously thought and the works performed are impressive, having achieved actual river captures, which makes this valley extremely important in the context of Roman mining in the north-east of the Iberian Peninsula," Javier Fernández Lozano, a geologist who worked on the project, told the Spanish language Information and Scientific News Service (SINC).
The researchers believe that the complex way the Romans stored and transported water in the mine was copied from the techniques used by the Egyptians. They’re now hoping to use LiDAR to find out more about the Roman mining practices in the area.
"Unlike traditional aerial photography, this airborne laser detection system allows the visualisation of archaeological remains under vegetation cover or intensely ploughed areas,” Fernández Lozano told SINC.
"Our intention is to continue working with this technique to learn more about mineral mining in the Roman Empire and clear up any mysteries such as why Rome abandoned such a precious resource as gold from one day to the next.”
And after that, El Dorado?