The Mysterious World of Caves and Caverns: Ancient Man's Home Sweet Home

2 of 11
deep sea cave photo
2 of 11

Caves can be found on every continent, within glaciers, and even, as seen here, under the oceans. Most simply, they are defined as a "natural underground space large enough for a human to enter."



Typically, a true cave has at least one portion that cannot be reached by natural light, though in common usage, a "cave" can include any opening into the earth.

Image credit: Kim Westerskov/Getty Images

WHAT'S HOT ON FACEBOOK