Carved out of the solid limestone of Capitan Reef by immersion in a bath of sulfuric acid some 5 million years ago, the Carlsbad Caverns National Park (575/785-2232, daily, $10 park entrance and self-guided tours, more for ranger-guided tours) contains over 119 underground caves, some 1,500 feet deep. A 1.25-mile trail drops steeply from the large visitors center, or you can board an elevator and ride 750 feet straight down to the Big Room, where the floor area totals more than eight acres. After wandering among the countless stalactites, stalagmites, and other formations, you can chow down on sandwiches at a snack bar.

The Big Room is only one of many cave formations protected at Carlsbad; some more delicate features can be found in the King’s Palace, and the park also has many more exotic and hard-to-reach caves (like Spider Cave, which you have to explore on hands and knees, or Slaughter Canyon, which is 23 miles away). These other caves can be enjoyed (if that’s the word) on the many longer guided tours (877/444-6777, $7-20, advance reservations recommended) available. These ranger-guided tours provide all the specialist caving gear (helmets, headlamps, knee pads, etc.) that you’ll need if you want to explore some of the more delicate features of the caverns or clamber around through more confined reaches of the caves.

Even if you just opt for the main cavern, be aware that the trail down to the Big Room closes early in the afternoon (usually around 3:30pm) so that visitors don’t interrupt the increasingly popular spectacle of the Bat Flight, in which hundreds of thousands of Brazilian free-tailed bats swirl out of the caverns at sunset. Every summer evening, rangers give a brief talk about bats (575/236-1374, around daily 7:30pm summer, free with park admission)—proselytizing about how great and harmless they are—while waiting for them to set off into the night. (You won’t catch sight of the bats here in winter, when they migrate to Mexico.)

Along Hwy-180 at the turnoff to the park stands White’s City Resort & Water Park (575/785-2291), a complex of motels, restaurants, pinball arcades, and souvenir shops. The most reliable places to stay and eat are 20 miles to the northeast, in the town of Carlsbad.