Half a mile of limestone passage in the Bear River Range above St. Charles, nine chambers of stalactites, flowstone and banded curtains, with fossils in the walls from the shallow sea this rock formed in. It sits at 7,700 feet up a canyon and holds around 40 degrees inside, so you want a jacket in August. There are 888 steps on the tour, which the guides will warn you about honestly. PUBLIC Forest Service tours in summer, Bear Lake County.
Idaho
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