Some interpretive tours in the national parks require more group participation than others. Take the visit to Balcony House in Mesa Verde National Park. The rangers actually ask you what kind of shape you're in and whether you're afraid of heights.

This photo explains why they want to know what you think of heights, as to enter Balcony House you have to scale this ladder. Once inside the cliff dwelling, there's at least one more, shorter, ladder you must climb, as well as a short, squat tunnel you have to exit through.

But the tour is well worth the effort, as you really gain a great appreciation of the construction skills of the Ancient Puebloans as well as an understanding of their desire for security. And the views into Soda Canyon are pretty grand, too.