The ruins of an 800-year-old Aztec pyramid were discovered by archaeologists in the central Tlatelolco area of Mexico City. The ruins are about 36 feet high and the archaeologists believe that the area could have been a major religious and political center. Fifteen years earlier, another pyramid was found at the site. Since then, historians have thought that Tlatelolco was founded by the Aztecs in 1325. The recent discovery is believed to have been built in 1100 or 1200 which means that the Aztecs could have begun to develop their civilization in the central Mexico mountains much earlier than believed.