The main pyramid, El Castillo, of Chichen Itza, Mexico was built with four stairways running from top to bottom of the pyramid's faces. The angle of the staircases was designed so that on the day of the equinox the sun's light produces what looks like an enormous snake slithering down the stairs.
“The snake of sunlightâ€, Chichen Itza, Mexico (©iStockphoto.com/CostinT)