A typical kiva is a circular, subterranean room, twelve to fourteen feet in diameter and seven or eight feet deep. Its walls are faced with stone to hold back the surrounding earth. At a height of about three feet from the floor the walls are stepped back so there is a ledge or shelf, at least a foot wide running entirely around the room. Resting on this ledge are six small masonry pillars, evenly spaced around the room, that support the roof. These pillars divide the space above the ledge into six recesses, the one to the south usually being deeper than the rest. The tops of the pillars are a couple of feet below the ground level and this space is built up with a cribbing of logs on which rests the roof of logs and adobe. The only door is a small hatchway in the center of the roof. The kiva is entered by means of a ladder which rests on the floor and extends up through the small door. This door is also the smokehole for directly below it in the center of the kiva floor is a firepit. Fresh air is brought into the room through a small, vertical shaft back of the deep recess on the south side of the kiva. The top of the shaft is a small opening in the courtyard while the bottom opens into the kiva just above the floor. As the smoke and hot air rise through the doorway fresh air is drawn down the ventilator shaft. Between the ventilator opening and the firepit is a small masonry screen, or deflector, that keeps the fresh air from blowing across the fire. On the other side of the firepit, opposite the deflector, is a small hole in the kiva floor, three or four inches in diameter and only slightly deeper. This small opening is of extreme importance to the priests. It is the sipapu, the symbolic entrance to the underworld. Many of the gods live in the Mother Earth and the prayers of the medicine men reach them through the small opening. The hole is merely a symbol. It represents the opening through which the Indians feel they themselves and all other living things emerged from the Earth Mother. The people believe the Sun is their father and the Earth their mother. After the union of the two, the people and all other creatures first came into being in a dark cave in the center of the earth, the world of darkness. After a time they climbed up to another cave where there was a little light. This was the world of twilight. For a short time they lived in this twilight world, then they climbed to another cave with still more light, the world of dawn. Finally, they emerged through a small hole in the earth, Sipapu, and were in the present world. All other creatures emerged just as they did; all life came from the Mother Earth.