Skulls are humanity's foremost symbol of death, and a powerful icon in the visual vocabularies of cultures all over the globe. Thirteen crystal skulls of apparently ancient origin have been found in parts of Mexico, Central America and South America, comprising one of the most fascinating subjects of 20th Century archaeology. 

© Joshua Shapiro photo by Vera Manaleo 

These skulls, found near the ancient ruins of Mayan and Aztec civilizations (with some evidence linking the skulls with past civilization in Peru) are a mystery as profound as the Pyramids of Egypt, the Nazca Lines of Peru, or Stonehenge. Some of the skulls are believed to be between 5,000 and 36,000 years old.