Visitors climb down the stairs in the archaeological area of the Quetzalcoatl Temple near the Pyramid of the Sun at the Teotihuacan archaeological site, about 60 km (37 miles) north of Mexico City April 22, 2013. A robot has discovered three ancient chambers at the last stretch of unexplored tunnel at Mexico's famed Teotihuacan archaeological site on Monday, the first robotic discovery of its kind in the Latin American country. Named Tlaloc II after the Aztec god of rain, the robot was first lowered into the depths of the 2,000-year-old tunnel under the Quetzalcoatl Temple to check it was safe for human entry. After months of exploration, the remote-controlled vehicle has relayed back video images to researchers of what appears to be three ancient chambers located under the Mesoamerican city's pyramid.[Photo/Agencies]

A visitor climbs up in the archaeological area of the Quetzalcoatl Temple near the Pyramid of the Sun at the Teotihuacan archaeological site, about 60 km (37 miles) north of Mexico City April 22, 2013. A robot has discovered three ancient chambers at the last stretch of unexplored tunnel at Mexico's famed Teotihuacan archaeological site on Monday, the first robotic discovery of its kind in the Latin American country. Named Tlaloc II after the Aztec god of rain, the robot was first lowered into the depths of the 2,000-year-old tunnel under the Quetzalcoatl Temple to check it was safe for human entry. After months of exploration, the remote-controlled vehicle has relayed back video images to researchers of what appears to be three ancient chambers located under the Mesoamerican city's pyramid.[Photo/Agencies]