At Mesa Verde National Park, if you're fairly fit and unafraid of heights, you can climb into history at the Cliff Palace.
It's one of the few cliff dwellings you can enter at the park, which is in southwest Colorado.
In fact, Cliff Palace is the park's largest cliff dwelling, with 150 rooms and 23 kivas (rooms for religious rituals) and probably housed about 100 people. The tour includes four ladders of 8-10 feet teach.
In honor of this year's National Park Service centennial, the Travel section is posting 100 park travel ideas and tips based on trips staff travel writer Christopher Reynolds has taken, along with photo-op advice from Times photographer Mark Boster. We'll post one per day through Dec. 31.
Follow Reynolds on Twitter: @MrCSReynolds