The Sun Stone (Aztec Calendar Stone)

A basalt disk nearly four meters across, carved in the last years of the Aztec empire, buried after the Spanish conquest and unearthed in Mexico City's main square in 1790. At the centre glares a face, the sun god Tonatiuh, or by some readings the earth monster, the tongue a sacrificial knife. Rings around it hold the signs of the days and the symbols of the previous world-ages the Aztecs believed had each ended in catastrophe. Despite its nickname it is not a working calendar but a cosmic diagram, the great emblem of Aztec Mexico.