Taken at Casa Grande National Monument. The ancient building is now under a protective cover. The ranger is describing the structure and its history. The walls are made of adobe from the topsoil of the desert. It must have taken quite a large group of people to excavate, form the adobe "bricks" and then erect the walls of this structure.

I have uploaded an image of grafitti on the ancient walls. It is located at:

www.ipernity.com/doc/2543754/51742608

If you are in Arizona, be sure to visit the National Monument.

www.nps.gov/cagr/index.htm

Image processed with GIMP.