Five thousand tunnels crisscross Cerro Rico, the "Rich Hill," which filled Spain's coffers until the silver reserves were exhausted in the early 19th century. Today tin is the primary extract, though on the barren mountainside you still see miners sifting through the remnants of ancient excavations. If you don't mind tight spaces, take a tour through one of the mines that are still active. You'll descend into the dark, humid tunnels where hundreds of workers strip down
to next to nothing because of the intense heat. Keep in mind that these mines are muddy, and wear clothes you don't mind getting dirty. Hard hats, raincoats, boots, and carbide lamps are provided, but take along a flashlight to get a better look at things. The extremely narrow entrance to the mine may scare you off, but go in far enough to give El Tío (a statue of a small, grinning devil) a cigarette and add more coca leaves to the pile around his feet. The miners say he brings safety and prosperity.