The first robotic exploration of a pre-Hispanic ruin in Mexico has revealed that a 2,000-year-old tunnel under a temple at the famed Teotihuacan ruins has a perfectly carved arch roof and appears stable enough to enter, archaeologists announced Wednesday.

Archaeologists lowered the remote-controlled, camera-equipped vehicle into the 12-foot-wide (4-meter) corridor and sent wheeling through it to see if it was safe for researchers to enter. The one-foot (30-cm) wide robot was called "Tlaloque 1" after the Aztec rain god.