While I was on vacation in New Mexico, I visited Chaco Canyon. Photographs can't convey the massive scale of the ruins, each of which would cover city blocks. Chaco Canyon was a ceremonial center of Southwest Indian culture, and was abandoned by 1250 AD, probably due to climate change. There are several huge pueblos with many kivas, and some of these structures have astronomical alignments. There is no point repeating everything in the excellent "Living the Sky" by Ray A. Williamson, which was recommended to me by Helen.
The first sight upon entering the National Monument section of Chaco Canyon is Fajada Butte. Unfortunately, it is now off limits. This site has a large spiral petroglyph behind stone panels with small slits between them. The light from solstices forms sun daggers on the petroglyph.
Pueblo Bonito, although 3 stories high, is dwarfed by the surrounding canyon walls.
The view towards Chetro Ketl and Pueblo Bonito from Casa Rinconada.
About 630 feet west of the cave is this propped boulder.