24 incredible underground attractions to visit in your lifetime

Some of the world's most breathtaking travel destinations may be hidden in the ground beneath your feet.

While some are man-made constructions, others are fascinating natural wonders that have been formed over the course of thousands of years.

We've put together a list of 24 subterranean attractions to visit in your lifetime, from a 10,000-year-old cave in Playa del Carmen, Mexico, to a town that built a library, church, bar, and homes underground.