The Ancestral Puebloans 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. It is believed that the Ancestral Puebloans developed, at least in part, from the Oshara Tradition, who developed from the Picosa culture. They 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. The Ancestral Puebloans 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.