Archaeologists announced Tuesday that they dug to the very core of Mexico's tallest pyramid and found what may be the original ceremonial offering placed on the site of the Pyramid of the Sun before construction began.

The city was founded nearly 2,500 years ago and came to have a dominant influence in architecture, trade and cultural in large swaths of ancient Mexico. But the identity of its rulers remains a mystery, and the city was abandoned by the time the Aztecs arrived in the area in the 1300s and gave it the name Teotihuacan, which means "the place where men become gods