Observational astronomy has deep roots in the Puebloan world of the Desert Southwest. Archaeological evidence suggests that the ancestral Pueblo Indians (Anasazi) marked astronomical events, perhaps as guides or records of their agricultural and ceremonial calendar. Rock art and architecture throughout the Four Corners area were carefully placed so that beams of sunlight would interact with rock images on important seasonal days such as equinoxes and solstices, marking the days with remarkably high precision.