Also called "dikengyuan" in Mandarin, which means "pit courtyards," the homes are a type of cave dwelling ("yaodong ... some of which have been modernized. Photos taken as recently as 2016 ...

One such drop is known as Fantastic Pit within Ellison’s Cave. It is the deepest freefall pit in America, plunging down vertically for 179 meters (586 feet). Within the same system is Incredible ...

Cutting a jagged path through the limestone of the Arabika massif on the edge of the Black Sea, the “trail” to Krubera Cave drops down a chain of pitches, cascades, and pits—some more than ...

Using radar images taken by Nasa's Lunar Reconnaissance ... acting as a convenient shelter for a lunar base. The cave is accessible through a pit in the well-studied Mare Tranquillitatis (Sea ...