Edward Thompson's 1904 diagram of Edifice 3, Chacmultun
"Edifice 3 is placed upon the same great general terrace as is the Palace, but upon a level about ten feet below that of the first story of that structure. So near is it to the Palace, in fact, that if the plan did not tell another story, one would be inclined to call it the first story of the Palace instead of a separate structure. The chambers of this edifice are much destroyed, and are of smaller size than those of the Palace just described, but they contain the most interesting portions of the entire group. It is in one of the rooms in this line of chambers, the one marked 10 in the ground-plan (Fig. 6), that I found the mural paintings shown on Plate VIII. Excepting the famous mural paintings of Chichen-Itza, these are the most nearly perfect of any yet found in northern Yucatan.
Chambers 1 and 3 of this structure have their roofs and the upper portion of their façades fallen in and so destroyed that a detailed description of their appearance would be useless. Their walls were originally more or less covered with paintings. Under the line of cornice outside and under the spring of the arch inside, portions of bright red and blue are still visible. Local excavations showed small raised platforms against the back walls.
Chamber 4 has its inner walls still perfect, and the roof is to a great degree still in place. The door to the chamber was buried under an immense mass of wall-stones and the debris of some large-sized structure that had fallen upon it from above. After much work the entrance was cleared. The chamber was of ordinary size, fourteen feet two inches long, ten feet six inches wide, and precisely twelve feet high. Opposite the entrance, extending entirely across the room and so large as to occupy nearly half the floor-space, was one of the platforms, or altars, before mentioned. As this is the most perfect one in this group, I shall attempt a somewhat detailed description of it. The top, or upper surface of the platform was made of stone and lime cement, a hard and smoothly finished surface running the entire length of the room and having a width of four feet six inches. It was faced by a band of smooth-cut stone six inches wide, and projecting four inches over the stone supports beneath it. These supports were each made of smooth blocks of stone, well cemented in their places and united overhead by large stones, each two feet four inches thick. This substructure supported the structure of the altar. In the centre of each of these supports is a carved head, or rather a mask of a human face, each different in character and decidedly different in expression. The first has a saturnine cast of features, and a large pair of canine teeth projecting over his under lip. The second had at one time some kind of a projection from the forehead, near the base of the hair, that extended down to and upon the nose. This adornment, attribute, call it what you will, has been broken off at some unknown period, carrying with it the nose and a part of the upper lip. The other two masks are too much defaced for description. Between these supports are large hollow cavities, each painted red inside, with rounded corners, extending under the platform. These curious platforms have been one of the unsolved problems which I have had constantly in mind ever since I first commenced my studies among these ruined groups. That they have some very general use is evident from the fact that they are a constant factor in all the ruined groups. Not all the chambers in all the groups have them, but I have yet to find a structure of any size without at least one chamber having one, and often two, one at each end.
Chamber 8 is the most perfect in condition of any yet found upon this tier. Upon the side opposite the entrance is a long narrow platform of the class above described. This chamber has an inner entrance connecting with a smaller chamber. Both of these rooms bear clear signs of having once had paintings upon their wall-surfaces. A leak in the roof immediately overhead and the consequent dampness is responsible for their almost utter destruction. In places the lines of color show forth with the greatest clearness, but this simply tantalizes the investigator, for no amount of patience can produce intelligible outlines.
The small inner chamber (9) has no features of special interest except that, small as it is, it has as many as six stone projections in the form of feet in various places upon the wall. Were these seen in the houses of to-day we should unquestionably call them hammock hooks, but as we have yet to learn that these people used hammocks, we can only say that they were probably used to suspend articles. Very few chambers, even those of considerable size, have more than four of these wall projections. It may be remembered that in my memoir upon the ruined group of X'Kichmook, I mentioned that one building in the group was furnished with the same kind of wall projections.
Continuing along the line of the façade and at right angles to the chamber just described, we reach the entrance to Chamber 10:6.
The Chamber of the Paintings Room 10: This chamber is fifteen feet long by ten feet two inches wide, and thirteen feet ten inches high. Directly in front of the entrance, facing the south and built against the rear wall, is a raised platform of cut stone and smooth, hard-finished floor-surface. It is the same character in structure as previously referred to. Upon all the walls of this room there have been mural paintings; even the vaulted ceiling bears traces of painted figures and colored designs; but the hard stucco that once covered both wall and ceiling has nearly disappeared, and only in places are traces still left to suggest the art treasures now lost. The rear wall, against which is built the raised platform, has portions of its surface in a measure preserved, and fortunately many of the figures are still so perfect that they can be faithfully copied (Plate VIII). Some portions of the roof ceiling, and of the walls as well, have been preserved from destruction by a thin coating of lime, incipient stalactites, which, while it veils the painted surface, yet affords us the satisfaction of knowing that the paintings are there, hidden under the lime coating. From the fragments of colored lines still in place, by reason of their sheltered position under the spring of the arch and just above the lintels, we are able to obtain some data unobtainable otherwise. Just above the spring of the arch are traces of a painted band six inches wide, having a centre of red and a clearly visible stripe of a purplish hue nearly an inch wide on each side. Each wall-space seems to have been divided into three bands, or zones, running horizontally, and on each wall the figures depicted upon each zone seem to have no connection with the other zones, except near the centre of the wall, where a complicated black figure runs from the third, or highest zone, down to the second, or middle zone, in a curious and apparently erratic manner. This subdivision into distinct zones, but joined in the centre by a curious figure, strikingly resembles the bas-relievos upon the wall of the lower chamber in the "Temple of the Tigers" in the Chichen-Itza group. The zones upon the different walls did not correspond, the one with the other, so far as could be seen, either in position or design, and the subjects depicted seemed to be distinct. Not only upon the inner surface of the lintels, but on the outer faces as well, were painted scrollwork designs in bright red and blue. Considerable traces of both these colors are yet clearly visible. The portions preserved best are directly under the deeply overhanging cornice, and to this circumstance the design owes it permanence. Some of these painted figures strikingly resemble portions of the Codices, but others, especially those in black, are unique among the mural paintings known to exist in Yucatan. Many of the figures have a slight resemblance to those of the ancient East."
E. Thompson, "Archaeological Researches in Yucatan" 1904: p. 13-16
Note: Some lovely old photographs taken in 1886-1889 by the archaeologist, Teobert Maler, are available online from the Peabody Museum of Harvard University and show how the building looked before it was cleared and consolidated.