El Castillo, Chichén Itzá, Mexico

Dominating the centre of Chichén Itzá is 'El Castillo' (the Castle), the Temple-Pyramid dedicated to the Feathered Serpent god, Kukulcan, the Maya name for Quetzalcoatl. On the Spring and Autumn equinox, at the rising and setting of the sun, the corner of the pyramid casts a shadow in the shape of a feathered serpent - Kukulcan, or Quetzalcoatl - along the side of the North staircase. On these two days, the shadows from the corner tiers slither down the northern side of the pyramid with the sun's movement.