GHENT, BELGIUM—A team of mining archaeologists has investigated a 5,000-year-old silver mine in Thorikos, Greece. The cramped mines were likely to have been worked by slaves, who endured the lack of light, fresh air, and temperatures that hovered around 70 degrees Fahrenheit. “The progress of the underground survey required a constant vigilance in this stuffy space where the rate of oxygen must be permanently watched,” Denis Morin of the University of Lorraine said in a press release. The team members have found tool marks on the walls of the subterranean galleries, graffiti, pottery, oil lamps, stone hammers, and crushing areas. By the fifth and fourth centuries B.C., silver was extracted on a large scale with a sophisticated system from shafts cut through the rock. For more on ancient silver mining, go to "The Environmental Cost of Empire."