From Boston to Denver, these cities have underground tunnels that you can explore, including this city in New Jersey.

In this adventure, we take an inflatable raft into a series of secret tunnels hidden deep in the wilderness. With only headlamps and a sense of curiosity, we float through dark, echoing passages not ...

Most people exploring a city focus on what’s above ground. But in several cities across the U.S., there's an entirely different story beneath your feet. These tunnels, ranging from historic ...

Editor's note: The following story was updated with new information. Want to go an adventure — underground? Then add exploring to your summer bucket list. There are so many treasures and wonders the ...