Think back to the joy you experienced in your childhood after digging in the ground and finding a small little treasure, even if it was just a malformed rock.

Researchers at Mexico's National University are feeling that glee on a much larger scale now that they've discovered an 1,800-year-old tunnel underneath the pre-Hispanic city of Teotihuacan.

Archaeologist Sergio Gomez Chavez of Mexico's National Institute of Anthropology and History calls the 130-yard-long tunnel a "representation of the underworld."

Researchers found symbols in the tunnel that lead to a funeral chamber at its end. If the chambers hold remains of Mesoamerican rulers like researchers believe, the find will be considered one of the most important archaeological discoveries of the 21st century.

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