_a._ Lower wall with doorway. _b._ Doorway. _c._ Wooden lintels. _d._ Communication doorway. _e._ Inner face of arch. _f._ Capstones of arch. _g._ Lower string-course. _h._ Decorated entablature. _i._ Upper string-course. _j._ Flying façade with ornament (sometimes added). _k._ Cornice of last. _l._ Roof-crest with ornament (sometimes substituted for _j_). (_After Holmes_)] [Illustration: FIG. 75.--Examples of Maya buildings. _a._ Single-chambered building. _b._ Multiple-chambered building. _c._ The round tower at Chichen Itza (restored). _d._ Building at Chichen Itza with sloping entablature of Palenque type. _e._ Palenque type of temple. _f._ The square tower at Palenque (restored). (_After Holmes_)] One of the principal features of Mayan architecture, as also Mexican, is the fact that all buildings of importance are constructed on raised foundations, varying in form from low platform mounds, often of irregular shape, to lofty pyramidal structures (Fig. 73). The two are not infrequently found combined, and a platform-mound sometimes supports a group of pyramids on which temples were erected. The sides of the platform-mound are sometimes given a steep slope, or are sometimes built vertical or nearly so, the latter form being characteristic rather of Yucatan. The pyramids are usually of the stepped variety, and the risers of the steps are frequently sloped; they are provided with a main stairway on one face, and sometimes with supplemental stairways on the other faces, as in the case of the so-called “Castillo” at Chichen Itza, which can be seen to the left of Pl. XXVIII; p. 348. In this building, and also at Copan, the stairway is furnished with ornamental balustrades, those at Chichen being carved in the form of two monstrous snakes of which the heads are extended on the ground at the foot of the pyramid. Practically all pyramid-mounds served as the support for buildings, though a certain number, without stairways, have been found which are simply burial-mounds. An exception occurs at Tikal (according to Tozzer), and perhaps in other places, where high pyramids with stairways appear to have had no crowning structures, and were possibly used as sites for offerings made in the open air. The material of which such structures are built is earth and rubble, and they have usually been faced with stone dressed with more or less accuracy, any imperfections being concealed with stucco. In some cases, notably at Copan, excavation has revealed the presence of a cement layer at some depth beneath the surface. This is probably an indication that the pyramid at some period has been enlarged, and it may be said that similar evidence of the practice of adding to existing structures is found elsewhere in the Maya area. The buildings which crown the foundation-mounds vary in type from simple, single-chambered edifices to elaborate complexes