A 3-foot long robot has revealed a network of complex tunnels under the largest Teotihuacan pyramid in Mexico. One of these underground chambers is filled with ancient artifacts.
The ancient city of Teotihuacan is officially dated to 2,500 years ago and was once one of the biggest cities on Earth with over 100,000 residents – though it is now becoming obvious that the site may have been ritually used before the Ice Age and the tunnels underground may actually be 20,000 years old.