Here's how to plan a visit to Kentucky's Mammoth Cave National Park, which is home to over 400 miles of underground passages, plus rivers and hiking trails.

Mystery Cave in Spring Valley, Minnesota, is one of those places that seems to exist in defiance of everything you thought you knew about what Minnesota looks like. Stone draperies hang like nature’s ...

The soda straw formations are another geological curiosity that sounds more like something from a diner menu than a cave feature. These thin, hollow tubes hang from the ceiling, formed by water ...