This is a reproduction of an Aztec calendar near Huelva in southern Spain. The original lies in a museum in Mexico City.
Based on meticulous astronomical observations, the Aztecs used this sunstone to determine whether the end of the world was near.
They found out it would happen on Dec. 21, 2012 — and weren't off the mark as far as this calendar is concerned. Just before the fateful date, someone destroyed several of its vividly colored tiles.