Long before James Franco grossed out moviegoers portraying an actual mountaineer's adventure gone wrong in 127 Hours, another real-life explorer found himself between a rock and a hard place with even more gruesome results. In 1925, cave explorer Floyd Collins got trapped 55 feet underground with his leg pinned under a boulder in Sand Cave, located near Mammoth Cave in Glasgow, KY. Attempts to rescue him created a media sensation, but Collins died after about 14 days underground.

Modern-day explorers can crawl, climb and squeeze more safely through the world's longest cave system on a variety of tours. Even the tour for non-death-defyers includes a segment known as "Fat Man's Misery," but thrill-seekers will want to go all out for the Wild Cave Tour, a 5 1/2-mile, "extremely strenuous" trip through the cave system's small passages and openings that are off limits on traditional tour routes.

For more information, tour Glasgow, KY in 36 hours.