FLAGSTAFF — Did you know Flagstaff is home to one of the largest lava tube caves in the country? The Lava River Cave in the Coconino National Forest stretches over a mile underground and was formed ...

Editor's Note: Due to the government shutdown, portions of the park might be closed or operating with limited staff. Please visit the National Park Service website for more information. There are ...

Sometimes, a hole in the ground is just a hole. Other times, it’s a portal to an underground cave spanning miles in width and length. You don’t really know what’s inside unless you dive into the void.

If human beings want to survive on the other planets for a long time, they must first find or set up a safe, stable, and long-term shelter. Lunar lava tubes are geological structures of the moon ...