Edward Thompson's 1904 diagram of Edifice 4, Xetpol Group
"Edifice 4 ...stands out imposingly like a fortress upon the sheer edge of a steep hill of solid naked limestone over a hundred feet high. The western face, fronting the steepest part of the hill, is almost perfect, the extreme north room only being unroofed; the other façades are in ruins. Seven entrances upon this façade look out upon the west. Four of these entrances open into suites of two chambers each, one behind the other. Each rear chamber is raised four feet above the floor of the front chamber and entered by a flight of stone steps, four in number.
Chamber 8 evidently had its walls more or less covered with designs of a scrollwork character, mostly line work done in a deep, almost purple, black. The fallen wall-surface has destroyed all hope of reproduction except around the doorway leading into the upper chamber. Here was found and copied the design given on Plate IX. The originals are drawn in strong even lines showing the master hand, and the artist about to copy them stood for some time in admiration of this vestige of the work of the prehistoric artist. Most of the rooms in this edifice have had their walls covered with designs in colors and in linework, but the black line work seems to have predominated.
Chamber 12, unlike those previously described, has the second room on the same level, and the entrance is from the left instead of in the direct rear. Both rooms have altars opposite their entrances. That in the first room is so destroyed that only its outline exists, but that in the inner room is a perfect as if made yesterday. It is faced with handsome cut and squared stones; the cement forming its upper surface is unusually thick, nearly six inches of mortar over the rubble filling. I found three apartments, or niches, beneath it."
E. Thompson, "Archaeological Researches in Yucatan" 1904: p. 17-18
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.