The ruins of Pueblo del Arroyo are shown in the valley floor at Chaco Culture National Historical Park, NM. Chaco Canyon was a major population center of the Ancestral Puebloans until its mysterious abandonment sometime around 1250 CE. Due to its cultural significance and unique architecture, UNESCO designated Chaco Canyon a World Heritage property in 1987. Click the above image to enlarge, or click to view my high-resolution photo gallery.