Archaeologists exploring tunnels under the Temple of the Feathered Serpent, a pyramid 30 miles from Mexico City, not only found three chambers (when they only expected one), but came across hundreds of mysterious metal spheres with unknown purpose.

Archaeologists Find Yellow Spheres on Ground in Chamber Under Temple of Feathered Serpent

The spheres found in a chamber off the tunnel seen on the ground. (Photo: DMC, INAH/M. MARAT via Discovery News)

According an article on Mexico's National Institute of Archaeology and History's website, the unexcavated portion of the tunnel under the temple in Teotihuacan was traversed by an infrared camera-equipped robot - Tlaloc II-TC -- that also had the ability to scan the area to generate a 3D picture.

Getting through the tunnel was a challenge with the robot because of its weight and the presence of mud, according to archaeologist Sergio Gómez Chávez. He said the wet conditions were to create a scene like that the Teotihuacanos believed to be similar to the underworld.

With information from the robot, archaeologists were able to find that they need to remove 30 more meters of debris in the tunnel to reach the three chambers.

Archaeologists Find Yellow Spheres on Ground in Chamber Under Temple of Feathered Serpent

One of the chambers in an already excavated portion of tunnel under the temple. (Photo: DMC, INAH/M. MARAT via Discovery News)

Two additional chambers that are within the already excavated portion of the tunnel is where archaeologists found the spheres, which they believe were placed inside at the last closing of the tunnel about 1,800 years ago.

"We can not yet establish its role because it is an unprecedented discovery. They should have a sphere, ranging from 4 to 12 inches and have a core of clay with organic matter, then covered them with pyrite, a mineral that underwent a process of oxidation and became jarosite, hence have a tone yellow," archaeologist Jorge Zavala said, according to the National Institute of Archaeology and History.

Archaeologists Find Yellow Spheres on Ground in Chamber Under Temple of Feathered Serpent

Spheres found in this chamber are on the ground. Archaeologists say in their original state, they would have shone as a golden color. (Photo: DMC, INAH/M. MARAT via Discovery News)

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Discovery News reported George Cowgill, professor emeritus at Arizona State University who has authored publications on Teotihuacan, saying the spheres in their original condition "would have shown brilliantly." Still, he said he had no idea what they could mean.

Gómez Chávez said the orbs would have appeared "metallic" at the time due to their properties.

The researchers hope the tunnels and chambers will offer clues about rituals, like burials of important figures, that were conducted in Teotihuacan.

"We believe that high-ranking people, priests or even rulers, went down to the tunnel to perform rituals," Gómez Chávez to Discovery News. "Maybe in this place, we will find the remains of those who ruled Teotihuacan."

See more pictures of the excavation in Discovery News here.

(H/T: Gizmodo)

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