Sitting Bull Crystal Caverns, Rapid City SD. Let the knowledgeable & friendly guides lead you through subterranean, crystalline passages in the Paha Sapa limestone. World’s most extensive display of dog-tooth spar crystal, some as large as 16″ in length. Peer into the still, clear water of Diamond Lake as it reflects the massive crystal ceiling like a giant mirror. French Chandelier room, Crystal Palace, Arch. You will feel as though you are walking through a giant geode.