A kiva is a room used by modern Puebloans for religious rituals, many of them associated with the kachina belief system. Among the modern Hopi and most other Pueblo peoples, kivas are square-walled and above-ground, and are used for spiritual ceremonies.
Similar subterranean rooms are found among the ancient peoples of the American southwest, including the Ancient Pueblo Peoples, the Mogollon and the Hohokam. Those used by the Ancient Pueblos of the Pueblo I Era and following, designated by the Pecos Classification system developed by archaeologists, were usually round, and generally believed to have been used for religious and other communal purposes. When designating an ancient room as a kiva, archaeologists make assumptions about the room's original functions and how those functions may be similar to or differ from kivas used in modern practice. The kachina belief system appears to have emerged in the Southwest at approximately AD 1250, while kiva like structures occurred much earlier. This suggests that the room's older functions may have been changed or adapted to suit the new religious practice.
As cultural changes occurred, particularly during the Pueblo III period between 1150 and 1300, kivas continued to have a prominent place in the community. However, some kivas were built above ground. Kiva architecture became more elaborate, with tower kivas and great kivas incorporating specialized floor features. For example, kivas found in Mesa Verde were generally keyhole shaped. In most larger communities, it was normal to find one kiva for each five or six rooms used as residences. Kiva destruction, primarily by burning, has been seen as a strong archaeological indicator of conflict and warfare among people of the Southwest during this period.
After 1325 or 1350, except in the Hopi region, the ratio changed from 60 to 90 rooms for each kiva. This may indicate a religious or organizational change within the society, perhaps affecting the status and number of clans among the Pueblo people.
Kivas are entered through a hole in the roof. A stone bench for sitting lines the inside wall, sometimes interrupted by support columns for the roof. Near the center of the kiva is a fire pit called a hearth. A ventilation shaft on one side supplies floor-level air for the fire. The ventilation shaft is generally located on the eastern side of the kiva.
They were entered by a roof hatch that also allowed smoke from the central hearth to escape. A ventilator shaft worked like a chimney in reverse, drawing in fresh air to feed the fire. A stone slab or low wall placed between the hearth and ventilator shaft defected the fresh air and reflected heat from the fire. Low pillars that rested on the bench circling the wall supported the roof.
There is usually a hole or indentation in the floor, now called a sipapu. Pueblo belief systems state that the sipapu symbolizes the connection from birth with Mother Earth . It may also represent the spot from which the original inhabitants emerged from the lower world .
Cajete and Nichols say that the Chacoan kivas were similar, and at the Aztec site's guide they also point out a rectangular room that was "remodelled into a kiva" (ibid).
Kivas were originally designed as water cisterns but may have later been used for ceremonial structures. As you might imagine that during a drought Indians may have gone inside the dry kivas and prayed for rain. Most kivas were refilled with collected rainwater. The standing stones were used to control the stirring up of silt when water was poured into the fireplace shaped inlet. Water was removed by carefully dipping pots in from the top where the cleanest water resided. I have personally seen the plaster and pitch residue that was used to seal the bricks. The bench like structure where they claim that people sit were actually a strong foundation like any modern dam needed to support the pressure of the water. All effective dams need to be thicker at the bottom. In the desert water is life, if kivas wern't cisterns, then where were the cisterns?
This may be the only picture of a 'kiva' in use:
Picture taken circa 1880