But now we had crossed the desert and had reached Chaco Culture National Historical Park, which for around 300 years constituted the center of the Ancestral Puebloan world. We had arrived on the evening of the summer solstice, and had experienced a kind of eerie night and beautiful solstice sunrise.
It was clear to the builders that a huge rock threatened the edge of the pueblo (we called the rock "Threatening Rock" in a fit of creativity). The Puebloans built a berm to try and stabilize the rock, and apparently they did a good job. It didn't collapse until 1941 (the pieces can be seen in the picture above).