"El Caracol" at Chichén Itzá has long been recognized as an astronomical observatory whose foundations are Maya and whose subsequent embellishments are Toltec. Perhaps the most significant alignments of this structure are those of its front door and its principal window, located just above it, both of which look out at the western horizon toward the sunset position on August 13.

The Maya were expert sky-watchers, careful observers of the motions of the celestial bodies. Proof of the Mayan fascination with astronomy is literally carved in stone in the grand architecture at sites such as Chichén Itzá, Uxmal, Uaxactun, Edzna, and dozens more. At many of these sites, hieroglyphic carvings refer to celestial bodies and cycles. Often, the buildings they adorn have been built to align with significant cyclical astronomical events—solstices, equinoxes, the shifting moon, or the rise of planets.

At Chichén Itzá, two structures bear witness to Mayan astronomy: El Castillo and El Caracol. Every year, tens of thousands of visitors flock to Chichén Itzá to see “the snake,” an apparition made of shadows that descends the stairs at El Castillo during the solar equinoxes each spring and fall. At El Caracol, dubbed “the observatory,” narrow shaftlike windows frame important astronomical events. One such window marks an appearance of Venus at a particular point on the horizon that takes place—like clockwork—once every eight years.  

"El Caracol" and  El Castillo at Chichén Itzá

"El Caracol" at Chichén Itzá