Mammoth Cave National Park, just a short drive from Glasgow, offers the chance to explore the world’s longest known cave system, with more than 400 miles of surveyed passageways.

The road to Fossil, Oregon, doesn’t reveal itself easily. After a wrong turn that had us questioning our navigation and a necessary stop at the ranger station in Ukiah for an actual paper map — no ...

The longest mapped network of caves in the world also contains one of the most implausible marine collections in North America. In Mammoth Cave, sharks and their kinsmen are preserved in layers of ...