Chichén Itzá

The amazing pyramid at Chichén Itzá is a physical representation of elements of the Mayan Calendar. It was designed so that on the solstice, light would descend from the top through the seven days and seven nights ending at the head of the serpent.

Here is a short noisy film on the descent of the serpent
http://www.youtube.com/watch?v=XK1Icq_fNRw&feature=related (link is external)