"It's very sexy, very atavistic," says Skip McWilliams, proprietor of the Sierra Trail Lodge in Creel, Mexico. He's gushing about his primordial cave fantasy, a ring-in-the-millennium travel package that one gullible couple can enjoy for only $6,500. The lucky twosome will bed down in a shallow rock hollow (once occupied by Tarahumara Indians) after spending New Year's Eve getting bombed with locals on a cactus-distilled moonshine flavored with drowned rattlesnake. "There are snake chunks floating around, but most guests love it," says McWilliams, who came up with the back-to-Bedrock concept while leading an ecotourism seminar in Copper Canyon a couple years ago. "I was trying to teach the less-is-more approach to travel." To emphasize his point, he threatened to stick a bed in a cave and rent it out. Attendees snickered, but he went ahead and found a rock dwelling behind his luxury lodge and began charging guests his usual nightly rate. Despite the utter lack of amenities—no door, no toilet—they scrambled for reservations.

Now he's marketing his high-dollar, low-overhead discovery with a vengeance and searching nearby box canyons for more caves to cash in on. At press time, the package—which also includes six nights at two of McWilliams's nearby man-made lodges—was still up for grabs. Call 800-776-3942 for details. Hurry, while the snake chunks last. —JILL DAVIS