At sunset, spectators gather at an amphitheater in this national park in southeastern New Mexico to wait for bats to fly. Predictably, a swirling dark cloud of the flying mammals funnels out the cavern and swoops above, where it splinters apart into groups heading to the nearby Pecos and Black River valleys. This rare natural show makes Carlsbad Caverns stand out from other national parks, especially to impress kids. Cave expeditions are also a draw, with rangers leading tours lasting from between an hour and a half and five and half hours. Some of the caves are huge, such as the well-named Big Room, which could fit 6.3 football fields. Adventurous kids will enjoy crawling through passageways or making rope-assisted descents through curtains of stalagmites, mentally soaking up all the educational lessons about geology explained by the rangers along the way. 575/785-2232, nps.gov/cave. Book ahead for guided tours. Entry fee: Adults, $6; kids under 15, free.