Carlsbad Caverns is a fairyland, an underworld marvel whose formations stun the senses. This remarkable geologic phenomenon began to take shape six million years ago. The processes and chemicals that created these caves were a unique combination—mainly an ancient limestone reef dissolved by sulfuric acid—and the result was unusual and dramatic compared to other caves. Huge rooms in random patterns, unpredictable dead-end passageways, pits and chimneys connecting different levels—these are the signatures of Carlsbad Caverns.