Cerro Rico (the Rich Mountain) and it's silver fueled the Spanish empire for half a century. The greed for silver made them send countless men into the Mountain that eats Men, the other name by which Cerro Rico is known. Today, little silver remains but with great hope the miners keep searching for it.
Many different agencies in Potosi take you on a tour of the silver mines. You suit up in miner outfits, buy some presents for the miners (choose the presents wisely), pay a tribute of tobacco and pure alcohol to the god that looks after the miners and enter the underworld. You go about 500 meters below sea level and experience first-hand the inhumane conditions that the miners work in. Occasional dynamite blasts in the mines wakes up the Mountain that eats Men. Chat with the miners to get an idea of their work and lifestyle. The entire tour lasts about 4 to 5 hours and cost 100 to 150 Bolivianos (~US$ 15-22)
Santa Cruz de La Sierra