Some of the oddest sites on our planet are below the surface.
See amazing footage from a drone fly-through of the Hang Son Doong cave in Vietnam, the largest in the world.
The microorganisms can survive underground despite the extreme dearth of light and nutrients.
A newly discovered species of reef coral hangs from the ceiling of undersea caves like a colony of petrified bats.
Scientists have found a stalagmite in an Oregon cave that tells the story of thousands of winters in the Pacific Northwest.
In the gloom of the caves and gorges of China, a plant has been discovered thriving in the dark.
A daring, death-defying race to find the planet's deepest hole is chronicled in a gripping new book.
White nose syndrome is devastating bats across eastern North America, and threatening local populations with extinction. Though there is no cure, researchers may have found a way to quell the carnage.