Yellowstone tourist dies in 500-foot fall

YELLOWSTONE NATIONAL PARK, Wyoming (AP) -- A woman lost her footing after stepping over a retaining wall to take a photograph and went over a cliff, falling 500 feet to her death in a canyon, Yellowstone National Park officials said.

(Retaining Wall: A wall of masonry used to keep soil or other material from in place, and from falling. A retaining wall (or bulkhead) is a structure to provide a barrier to downslope movement of soil, rock, or water. {Or humans?})