Mention an ancient city of pyramids shrouded in mystery ... Teotihuacan was a thriving urban center and religious site of the warlike Aztec Empire, but the Aztecs were not its first inhabitants.

Archaeologists have discovered the ruins of an 800-year-old Aztec pyramid in the heart of Mexico ... find soon should tell us much more about the society of Tlatelolco," said Ledesma.

Archaeologists in Mexico found nearly 200 animal remains beneath the Moon Pyramid in Teotihuacán ... more than a millennium before the Aztec civilization settled in the region.