I have been in a (long, long unused) kiva at Chaco. Actually, I've been in several, some of which were unroofed. They are round rooms with a ledge around the inside for sitting, some have two ledges in a step fashion. You enter and leave through what also functions as the smokehole. Kivas were and are sacred to different groups, although some are shared. Usually those entering had to take a sweat bath first.