This story appears in the August 2010 issue of National Geographic magazine ... They built up during ice ages, when the sea level dropped dramatically, leaving the caves dry.

This story appears in the March 2017 issue of National Geographic magazine ... in mapping new parts of the cave and collecting scientific data. Ice crystals populate Full Moon Hall.

More info: NatGeo.Com In Bongolo Cave ... for National Geographic A young emperor penguin jumps off a 50-foot cliff for its ...