Overview: Travel to the deepest place on Earth, Johannesburg, South Africa's Mponeng Gold Mine. South Africa's economy depends on gold, but recently, productivity has plummeted. Now, Mponeng is fighting back by digging deeper than man has ever gone, towards an untapped gold reef worth $10 billion. Setting a new depth record every day, workers blast through super-heated rock nearly 3 miles down, in the most remote and dangerous construction site on the planet.