"At Río Bec, on the other hand, the pseudo-pyramid presents a much taller outline, as if it were coming out behind a gigantic "steam roller," and its stepped structures, which narrow slightly toward the tops, have an unmistakable aspect with their carefully rounded corners and their delicate mouldings that gird each entity both on the base and the upper part. This creates a very subtle rhythm in which the principal wall stones -- almost vertical -- seem to cross the thin band above and visually continue into the base of the next section.
...It should be noted that the steps of the simulated stairway, in order to permit ascent to the top, are often cut in saw-tooth fashion, which provides a space scarcely sufficient to put the toes, and along the central axis of these stairways large masks, niches, or stylized huts are cut out." p>
Paul Gendrop, Rio Bec, Chenes, and Puuc Styles in Maya Architecture, p. 40-43