02Carlsbad Caverns, New Mexico

Carlsbad Caverns is a national park with a vast network of underground caves. The 'Big Room' spans 8.2 acres, and narrow passageways lead to stunning views of the Spider Cave and the Hall of the White Giant. The Natural Entrance offers incredible views looking down from the greenery of the park into the caves. However, the trail into the caverns is steep and accessible only to accomplished hikers.

Carlsbad Caverns elan7t50 / Getty Images