One of the most intriguing features of this monument is the optical illusion on two yearly equinoxes when the play of light and shadow on the northern staircase represents the shape of a serpent which descends along the steps to join the serpent head at the base. According to Mayan legend, this magic represents god Kukulcan returning to earth to commune with his worshipers, provide a blessing for a full harvest and good health before entering the sacred water, bathing in it, and continuing through it on his way to the underworld.Legends aside, Fabio later describes what actually happens on those two days when time span of day and night are equal.The mathematically astute architecture of the pyramid combines with the earth’s natural rotation to create a somewhat peculiar image of a giant snake crawling down the temple.For almost five hours this trickery of light and shadow displays seven triangles on the side of the staircase starting at the top and inching its way down until it connects the top platform with the giant stone head of the feathered serpent at the bottom.Then, for almost an hour this extraordinary shadow stays in its entirety before descending the pyramid.
