Also known as The Palace, the Temple of Five Stories "faces west and is aligned so that on May 1st and August 13 -- when the sun reaches its zenith at this location -- the setting sun blazes directly into its rooms. This alignment is probably related to planting times."
Coe, Andrew, "Archaeological Mexico", p. 302
A central stairway, which has been restored only on the left side, ascends the west face to the fifth level temple below the tall, partly ruined roof comb. The small temple at the top contains three rooms; the back wall of the central room contained a stela, now removed, which was illuminated by the rays of the setting sun at its zenith.