Carlsbad Caverns (United States)

The Doll's Theater in Carlsbad Caverns is one of the cave system's stunning features.

Photo courtesy of NPS

Carlsbad Caverns National ParkNew Mexico, United States

A whole other world lies beneath the Guadalupe Mountains in Carlsbad, N.M. It took millions of years to produce the enormous underground rooms that draw visitors to Carlsbad Cavern National Park from around the world.

With three known levels, at 750 feet (229 meters), 900 feet (274 meters) and 1,350 feet (411 meters) below ground, respectively, there's plenty for those visitors to experience [source: NPS]. The caverns seem decorated with some of the most stunning cave features around, including the Giant Dome, a column measuring 62 feet (19 meters) tall and 16 feet (5 meters) in diameter, and the Frozen Waterfall, a stone creation that bears an uncanny resemblance to its namesake [source: NPS]. There are stalagmites and stalactites of every shape and size, as well as basins lined with onyx crystals.

Still, perhaps the most shocking aspect of the Carlsbad cave system is its size. A single chamber in Carlsbad Caverns, aptly named the Big Room, measures 4,000 feet (1,200 meters) long and up to 625 feet (190 meters) wide and 350 feet (107 meters) tall [source: NPS]. And that's just what's been discovered so far: The caverns are still being explored and uncovered.

Up next: a cave of unimaginable dimensions.