APTOPIX Mexico Aztec Skull Rack

In this May 30, 2015 photo released by Mexico's National Institute of Anthropology and History (INAH), skulls are partially unearthed at the Templo Mayor Aztec ruin site in Mexico City. INAH archeologists believe they have found the site's main trophy rack of sacrificed human skulls, known as "tzompantli," where Aztecs displayed the severed heads of sacrificial victims on wooden poles pushed through the sides of the skull, but that this one is different. Part of the platform where the heads are displayed is made of rows of skulls mortared together roughly in a circle, but experts don't know what was at the center of the circle. (Hector Montano/INAH via AP)