10 Incredible Holes

Savuka Mine
Miners walk through the Savuka gold mine in South Africa. © Michael S. Lewis/CORBIS

South Africa is home to the world's largest gold deposit, which lies in deep seams running southwest from Johannesburg. Mining the valuable mineral is a big business in this country, accounting for an impressive 20 percent of its total exports. In recent years, however, surface deposits have all but dried up, forcing mining companies to dig deeper and deeper into the ground. For this reason, South Africa is home to the world's deepest gold mines, including the Savuka Mine in West Rand, which descends to a stunning depth of 2.35 miles (3.78 kilometers) [source: Bridgland]. As of 2007, this was the deepest mine in the world; however, Savuka's parent company, AngloGold Ashanti, has plans to extend the nearby TauTona mine to 2.4 miles (3.9 kilometers), though the current progress on that project is unclear [source: Wadhams].

While mining at such depths is a remarkable feat, it's extremely dangerous. Temperatures at these depths rise well above 100 degrees Fahrenheit (55 degrees Celsius) -- so hot, in fact, that miners have to wear special jackets packed with ice when working there [source: Wadhams]. Earthquakes are also a concern. In May 2009, a pump attendant at the Savuka mine lost his life during a seismic event, causing the mine to shut down over safety concerns. Over the last 100 years, 70,000 South African miners have died underground and more than one million have been seriously injured [source: Brigland]. With such hellish conditions in the deep mines like Savuka, it's no wonder workers often describe the shafts as the "devil's workplace."