For hundreds of years, workers broke and hauled salt out of the Salina Turda mine in Romania. That stopped in the 20th century. Since 1992, the huge chambers left behind have been a tourist attraction, which became a full-fledged theme park in 2010. The features include a 65-foot-tall Ferris wheel, an amphitheater, bowling alleys, a miniature golf course, and a lake where you can ride a boat, all contained in the huge underground chambers.
via Neatorama
Image: Cristian Bortes