How times have changed. These days when you drop down into the underworld that is Carlsbad Caverns National Park you do it via stairs, not old guano buckets as was the custom early on in the park's history.

One of the most intriguing interpretive tours I’ve joined across the national park system was the “wild cave tour” offered at Mammoth Cave National Park. For six or more hours in sections of the cave off-limits to the more traditional tours we scooted through tight places on our bellies when not able to get by on hands and knees.