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. The gemstone skulls supplied by The Wizard of Auz are not ancient, although they draw on the symbolism and mysticism that intrigues and endears us as humans to this most primal of objects.