Today, it is difficult to imagine the extreme conditions in which the miners had to work in this maze of galleries. A smothering heat reigns in this mineral environment. The progress of the underground survey requires a constant vigilance in this stuffy space where the rate of oxygen must be permanently watched. Tool marks on the walls, graffiti, oil lamps, and crushing areas give evidence of the omnipresent activity of these underground workers. The hardness of the bedrock and the mineralizations show the extreme working conditions of these workers, for the greater part slaves, sentenced to the darkness and the extraction of the lead-silver ore ... Mapping these cramped, complex and braided underground networks, the ramifications of which are sometimes located at several levels, represent a real challenge in scientific terms.The finds include stone tools and pottery which may date as early as 3200 BCE, which would be remarkable if it turns out to be true.
The Greeks regarded mining as so miserable and dangerous that of course only slaves would do it; I think that if you had told an ancient Greek that we have a society without slavery, he would have said, "But who works the mines?"