In the Colorado Plateau area of the American Southwest there are numerous old structures and cliff dwellings from an ancient civilization. The people that inhabited this area were know as the Anasazi Indians. Most every canyon in the region hold some form of markings (petroglyph) or structure left behind by these early Indian tribes. It is a fascinating place to hike and explore the remains of an ancient civilization. It is important to use extreme caution when hiking into these locations not to disturb or alter any of these old sites. I have found over the years that most people that have the desire to explore such regions do so with great respect and try to avoid impacting the area as much as possible.
http://cpluhna.nau.edu/Places/places.htm
http://pages.towson.edu/brenda/newmexico/anasazi.htm
http://www.indians.org/articles/anasazi-indians.html