The chief peculiarity of these ruins, that which especially invites attention, is the evidence they furnish that their builders had remarkable skill in architecture and architectural ornamentation. All who have visited them bear witness that the workmanship was of a high order. The rooms and corridors in these edifices were finely and often elaborately finished, plaster, stucco, and sculpture being used. In one room of a great building at Uxmal Mr. Stephens says “the walls were coated with a very fine plaster of Paris, equal to the best seen on walls in this country.” Speaking of the construction of this edifice, he says, “throughout, the laying and polishing of the stones are as perfect as under the rules of the best modern masonry.” All the ruins explored have masonry of the same character. The floors, especially of the courts and corridors, were made sometimes of flat stones admirably wrought and finely polished, and sometimes of cement, which is now “as hard as stone.” Mr. Stephens, describing corridors of the “Palace” at Palenque, says “the floors are of cement, as hard as the best seen in the remains of Roman baths and cisterns.” We give two illustrations of their method of constructing the arch. Figure 25 shows an arch of Las Monjas, at Uxmal. Figure 26 shows the most common form of the arch in the older ruins. [Illustration: Fig. 26--Common Form of Arch.] The ornamentation is no less remarkable than the masonry and architectural finish. It is found on the walls within and without, and appears in elaborate designs on the heavy cornices. The exterior ornamentation is generally carved or sculptured on the smooth surface of the stone, and must have required a vast amount of time and labor, as well as skillful artists. In some of the ruins inscriptions are abundant, being found on walls, tablets, and pillars. The general effect of the exterior decoration is thus described by Mr. Stephens in the account of his first view of the ruins at Palenque: “We saw before us a large building richly ornamented with stuccoed figures on pilasters, curious and elegant; trees growing close to it, and their branches entering the doors; the style and effect of structure and ornament unique, extraordinary, and mournfully beautiful.” In a description of the walls around an interior court of a building at Uxmal, we have this tribute to the artistic skill of the decorators: “It would be difficult, in arranging four sides facing a court-yard, to have more variety, and, at the same time, more harmony of ornament.”