Oak Tree House has seven kivas and may be called a large cliff dwelling. One of the kivas has a semicircular ground plan with a rectangular room on the straight side. There are no pilasters or banquettes in this kiva. The floor of another kiva was almost wholly occupied by a series of grinding bins, indicating a secondary use. The excavation work on Oak Tree House has not yet been completed, but a small collection of specimens at one end of the ruin shows the nature of the objects thus far found. SUN SET HOUSE Looking across Cliff Canyon from Sun Point one can see the fine ruin called Sun Set House, formerly known as Community House. This ruin, like many other cliff dwellings, has an upper and a lower house, the former being relatively larger than is usually the case. Although Sun Set House is accessible, it has never been excavated. SUN TEMPLE The cliff houses considered in the preceding pages are habitations. There are also specialized buildings on the Mesa Verde which were never inhabited but were used for other purposes. Two of these presumably were devoted solely to ceremonial purposes and are known as Sun Temple and Fire Temple. Sun Temple is situated west of Cliff Palace, on the promontory formed by the confluence of Cliff and Fewkes Canyons. Up to the year 1915 the site of Sun Temple was a mound of earth and stones, all showing artificial working or the pecking of primitive stone hammers. This mound had a circular depression in the middle and its surface was covered with trees and bushes. No high walls projected above the ground nor was there any intimation of the size or character of the buried building. It was believed to be a pueblo or communal habitation. Excavation of this mound brought into view one of the most unusual buildings in the park. Sun Temple is a type of ruin hitherto unknown in the park. The building excavated shows excellent masonry and is the most mysterious form yet discovered in a region rich in prehistoric remains. Although at first there was some doubt as to the use of this building, it was early recognized that it was not constructed for habitation, and it is now believed that it was intended for the performance of rites and ceremonies; the first of its type devoted to religious purposes yet recognized in the Southwest. The ruin was purposely constructed on a commanding promontory in the neighborhood of large inhabited cliff houses. It sets somewhat back from the edge of the canyon, but near enough to make it clearly visible from all sides, especially the neighboring mesas. It must have presented an imposing appearance rising on top of a point high above inaccessible, perpendicular cliffs. No better place could have been chosen for a religious building in which the inhabitants of many cliff dwellings could gather and together perform their great ceremonial dramas.