Tourists are seen in front of the "Gran Jaguar" Mayan temple at the Tikal archaeological site in Guatemala, where ceremonies will be held to celebrate the end of the Mayan cycle known as Baktun 13 and the start of the new Maya Era on December 21. Johan Ordonez/AFP/Getty Images hide caption

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A replica Mayan Calendar Round showing the date September 21, 2004, opening day for the Smithsonian's National Museum of the American Indian. Molly Stephey/Smithsonian's National Museum of the American Indian hide caption

toggle caption Molly Stephey/Smithsonian's National Museum of the American Indian