Bolivian miners having been digging for silver in the mountain of Potosi for 400 years. Hundreds of thousands have died and yet more still keep going down, even today. They get a little extra money from tours led by ex miners bringing visitors to gape at how difficult and dangerous their daily work is. My 9 year old daughters and I took such a tour and left with a renewed appreciation of how lucky we are not to have to live by such hard labor. Scrambling through minuscule paths cut through solid rock, dropping into open pits lit only by the headlamp on your helmet, breathing in dust and asbestus, it is a world where workers worship Tito, the Devil god of the underworld for their own protection.
Tip - make sure you do not sign up with any agency that sets off explosives for the tourists' amusement and make sure that a percentage of your fee is returned to the mine workers.