Murfreesboro Diamond Mine, Arkansas

Said to be the only publicly-accessible diamond mine in the world, this mine was turned into a tourist attraction by the state in 1971, and renamed Crater of Diamonds State Park. For an admission price of eight dollars for adults, people can (and do) scour the almost 40-acre site to look for diamonds, keeping what they find. In 1924, the 40.23-carat Uncle Sam diamond was found at the site, which remains the largest diamond ever found in the United States.