12. Carlsbad Caverns – New Mexico
This national park is home to over 100 caves built out of limestone and carved with natural sulphuric acid. Established in 1930, the caverns have a natural entrance that visitors can walk (via Buzzfeed). One location is called the Big Room and features magnificent stalactites growing from the ceiling. If caverns aren’t your thing, you can choose to drive through the Rattlesnake Springs instead, where you can see reptiles and hundreds of bird species native to the area (via Buzzfeed).