ncestral Puebloans, also known as the Anasazi, were an ancient Native American culture that spanned the present-day Four Corners region of the United States, comprising southeastern Utah, northeastern Arizona, northwestern New Mexico, and southwestern Colorado. The people and their archaeological culture are often referred to as "Anasazi". This, meaning "ancient enemies", was the name they were called by Navajo, who are not their descendents. Contemporary Puebloans object to the use of this term. The Ancestral Puebloans are believed to have developed, at least in part, from the Oshara Tradition, who developed from the Picosa culture. The Ancestral Puebloans lived in a range of structures that included small family pit houses, larger structures to house clans, grand pueblos, and cliff-sited dwellings for defense. They possessed a complex network that stretched across the Colorado Plateau linking hundreds of communities and population centers. They held a distinct knowledge of celestial sciences that found form in their architecture. The kiva, a congregational space that was used chiefly for ceremonial purposes, was an integral part of this ancient people's community structure. Archaeologists continue to debate when this distinct culture emerged. The current agreement, based on terminology defined by the Pecos Classification, suggests their emergence around the 12th century BC, during the archaeologically designated Early Basketmaker II Era. Beginning with the earliest explorations and excavations, researchers identified Ancestral Puebloans as the forerunners of contemporary Pueblo peoples. Three UNESCO World Heritage Sites located in the United States are credited to the Pueblos: Mes