Located nine miles south of
Rapid City, this is one of the few caves in the world with the hexagonal calcite crystals called dogtooth spar, some specimens as large as 16" long. The spar, occurring in leafy clusters, is reflected in the natural pool in one of the cavern's many corridors. The underground Diamond Lake reflects the cave's massive crystal ceiling; other natural formations include the French Chandelier room, Crystal Palace, Rainbow Arch, and the Petrified Fish Crevasse, a 110-foot-long natural rock hall embedded with fossilized prehistoric marine life.
The site's visitor center and cave entrance are located about 10 minutes south of Rapid City in Rockerville Gulch, a scenic canyon east of Rockerville ghost-town, a historic site from the gold mining days of the late 1800's. Cave open daily, 45-minute tours leave every 20 minutes.