While a cave might not sound quite as sexy as redwoods, geysers or the Grand Canyon, there’s no question that this one measures up on the national parks’ jaw-droppingly ginormous scale: to simply reach the main chamber, you have to either take an elevator that drops the height of the Empire State Building or, more enjoyably, take a spooky 1.25-mile subterranean walk that goes down and down (and down) from the cave mouth into the yawning darkness.
Either way, you’ll find yourself in the aptly named Big Room, an underground room 1800ft long (that’s the equivalent of 11 American football fields), 255ft high and over 800ft below the surface, where you’re free to walk an intricate loop trail (1.25 miles) past a pick of amazing sights, including the world’s largest stalagmite and the ever-popular Bottomless Pit. Wear a sweater: the temperature is 56°F (13°C) year-round.
In addition to the self-guided tour, the park service runs a number of daily guided tours – advance reservations are essential. They are all excellent and highly informative, providing visitors with access to otherwise closed portions of the cavern, or real spelunking adventures in some of the backcountry caves like Slaughter Canyon. Plus, your guide will inevitably turn out the lights at some point – sitting hundreds of feet below ground in the pitch black is an experience you’re unlikely to forget.
The cave's other claim to fame is the colony of approximately 400,000 Mexican free-tailed bats that roosts here from mid-April through October. Wait at the cave mouth at sunset to watch them cyclone out for an all-evening insect feast. A free Bat Flight ranger talk occurs nightly from late May.
With 30 miles of passages and the largest subterranean chamber in the US, it’s hard to get your head around just how big Carlsbad really is. But consider this: Carlsbad is only one of 120 known caves within the park’s borders, and the largest, Lechuguilla, extends for some 136 miles, dropping to a depth of 1600ft. Unfortunately, it's only open to research and exploration teams, with special permission from the park.
If you’d like to explore the Chihuahuan Desert above ground, pick up a permit (free) for a backpacking trip at the visitor center along with a topo map of the 50-plus miles of hiking trails. November to March is the best time for backpacking – summer temperatures are scorching, while the countless rattlesnakes should be sleeping in winter. The visitor center has a small cafeteria, where you can have a simple lunch. There's also an underground snack counter beside the Big Room, but no food or drinks are permitted in the cave beyond the small dining area. There are restrooms beside the Big Room too.