"The ancient city of Teotihuacan lies north of modern Mexico City. It remains largely a mystery, and was so even for the Aztecs, who are credited with founding Mexico City in the 1300s.

Teotihuacan, one of the largest cities in the world around the time of Christ, had an estimated 150,000 inhabitants, and influenced art and architecture as far away as the Yucatan peninsula. However, it had been abandoned and crumbling for centuries by the time of the Aztecs.

The artifacts discovered Wednesday may push the date of Mexico City's founding back to the classic Teotihuacan period of 300-600."