This formation, consisting of limestone, and some layers of clay and coal, is the major landmark of the Chaco Canyon area. It is visible for miles on the approach roads. It rises more than 400 ft above the valley floor.

It has a considerable history as a shrine, place of worship, and astronomical observatory. It contains a solar calendar, various petroglyphs, and former rooms under cliff overhangs. These rooms are thought to have been used by Chacoan astronomers. There is even an eagle's nest which has been active in recent years.

It is still viewed as a sacred shrine by some groups of Pueblo and Navajo Indians, who claim descent from, or kinship with the Chacoan builders.