The metal balls were found in a Teotihuacan pyramid in Mexico.

The orbs were made from a core of clay and are covered with a yellow material called jarosite. One of the archaeologists who found them told Discovery News “they look like yellow spheres, but we do not know their meaning. It's an unprecedented discovery.”

It’s thought Teotihuacan came into being around 100 AD near what is now Mexico City.

It was left vacant 700 AD and was one of the biggest and most progressive cities of its time.

Archaeologists used robots and infrared cameras with scanners to explore small tunnels that were believed used by priests for ceremonies. They called the area the "Temple of the Feathered Serpent."

Excavation has begun on the last of the tunnels and chambers with high expectations for what may be found there.

One researcher revealed that "the area is still in remarkable condition and has not seen a human in almost two millennia." 

"Can you can imagine” he began. “What can be found inside?"

More here.