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 on the moon ...

Another world greets you just a short 30-minute drive from the Icelandic capital Reykjavik. Raufarhólshellir Lava Tunnel is a terrific example of a lava cave created following a volcanic eruption ...

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.