Pyramid wall with relief at Tenayuca in the Valley of Mexico.

Pyramid wall with relief of Xiuhcoatl the Aztec Serpent God of the Sun. The relief at Tenayuca forms part of a pre-Columbian, Mesoamerican archaeological site in the Valley of Mexico. In the Post classic period of Mesoamerican chronology. By some historiographic traditions Tenayuca had been founded ca. 1224 by Xolotl, a semi-legendary ruler of a "Chichimec" tribe. Aztec temple architecture primarily developed at Tenayuca, which has the earliest example yet found of the typical Aztec double pyramid, which consists of joined pyramidal bases supporting two temples. The base of the Aztec pyramid of Tenayuca is adorned with a row of rattlesnake sculptures, known as coatepantli in Nahuatl. (Photo by: Universal History Archive/Universal Images Group via Getty Images)