A comparison between Pl. VIII and Pl. XIII shows at once that the inhabitants of the Cliff Palace were further advanced in architecture than their more western kinsfolk on the Mesa Verde. The stones are carefully dressed and often laid in regular courses; the walls are perpendicular, sometimes leaning slightly inwards at the same angle all round the room--this being part of the design. All the corners form almost perfect right angles, when the surroundings have permitted the builders to observe this rule. This remark also applies to the doorways, the sides of which are true and even. The lintel often consists of a large stone slab, extending right across the opening. On closer observation we find that in the Cliff Palace we may discriminate two slightly different methods of building. The lower walls, where the stones are only rough-hewn and laid without order, are often surmounted by walls of carefully dressed blocks in regular courses. This circumstance suggests that the cave was inhabited during two different periods. I shall have occasion below to return to this question. The rooms of the Cliff Palace seem to have been better provided with light and air than the cliff-dwellings in general, small peep-holes appearing at several places in the walls. The doorways, as in other cliff-dwellings, are either rectangular or T-shaped. Some of the latter are of unusual size, in one instance 1.05 m. high and 0.81 m. broad at the top. The thickness of the walls is generally about 0.3 m., sometimes, in the outer walls, as much as 0.6 m. As a rule they are not painted, but in some rooms covered with a thin coat of yellow plaster. At the south end of the ruin lies an estufa (93) which is well-preserved (fig. 37). This estufa is entered by a doorway in the wall, one of the few instances where I have observed this arrangement. In most cases, as I have already mentioned, the entrance was probably constructed in the roof. The dimensions of this estufa were as follows: diameter 3.9 m., distance from the floor to the bottom of the niches 1.2 m., height of the niches 0.9 m., breadth of the same 1.3 m., depth of the same 0.5 to 1.3 m., height of the passage at its mouth 0.75 m., breadth of the same 0.45 m. Five small quadrangular holes or niches were scattered here and there in the lower part of the wall.