National Geographic News

Iron Hoop Cave, Alabama

Photograph by Stephen Alvarez

Millennia in the making, fantastical chambers like this are decorated by the infinitely slow accumulation of minerals (chiefly calcite) deposited by water dripping through rock. Encounters with such rare and fragile beauty are highly prized.

See more photographs from the June 2009 National Geographic feature story "Deep South."

Buy a print of this photo.

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