Pueblo ceremonial chambers are known as kivas (the Hopi name) or estufas (the name applied to them by the Spaniards under the misapprehension that they were sudatories). They are circular or rectangular, wholly or partly subterranean, or simply cells in the communal structure that forms a pueblo. The character of the underlying soil or rock was probably the factor that determined the degree to which a kiva was made subterranean. The one here illustrated is mostly underground, and has a walled stair leading to the roof, which is surrounded by a parapet. Similar structures have been found in excavating ruined pueblos. (See Volume XVII, illustration facing page 68.