Native Americans always knew there was a giant cave system snaking around under the porous limestone reef of the Guadalupe Mountains. But white settlers only stumbled upon it a century ago, after noticing vast hordes of bats swarming out of a hole in the ground every summer day at sunset. Some 100 caves lie within today's park, an underground world of pale limestone, where every fantastic and grotesque shape imaginable (and unimaginable) has been sculpted by natural forces -- from frozen waterfalls to strands of pearls, soda straws to miniature castles, draperies to ice-cream cones. Above all, what is impressive here is the sheer size of the cave, a constantly cool (56°F/13°C) refuge from the 100°F (38°C) heat outside in the Chihuahuan Desert.
The main cave open to the public, the immense Carlsbad Cavern, offers several options. With smaller kids, you may just want to take the elevator from the visitor center down 750 feet to the Big Room, which is a pretty understated name for this jaw-dropping rock chamber whose floor covers 14 acres. If you're more ambitious, follow the traditional explorer's route from the historic natural entrance, winding down for a mile into the depths through a series of underground rooms to the same Big Room. A self-guided tour from here runs 1 1/4 miles over a relatively level path, taking about an hour. Rangers along the path point out some of the more evocative formations, demonstrating the still-growing dome stalagmites and the daggerlike stalactites jabbing down from the ceiling.
Tours of other sections of Carlsbad Cavern range from the easy Left Hand Tunnel, a half-mile lantern tour, to the difficult Hall of the White Giant, which requires you to crawl long distances, squeeze through tight crevices, and climb up slippery flowstone-lined passages. The 2 1/2-hour tour of Slaughter Canyon Cave is a far more strenuous cave hike from a different cave mouth altogether, about a 45-minute drive from Carlsbad Caverns. (Visitors to Slaughter Canyon Cave will need to first pick up tickets at the Carlsbad Caverns Visitor Center.) And if the kids don't like being underground too long, they can still join one of the most popular activities at the caves, a sunset gathering at the natural entrance (May–Oct) to watch a quarter-million Mexican free-tailed bats flap out of the cavern to wheel out over the desert for a night of insect feasting. After all, that's how the Americanos found the joint in the first place.
Nearest Airport: Cavern City, 23 miles. El Paso International, TX, 150 miles.
Where to Stay: $$ Rodeway Inn, 6 Carlsbad Cavern Hwy., Whites City (tel. 800/CAVERNS [228-3767] or 575/785-2296; www.rodewayinn.com).