Archaeologists Are Unlocking a 1900-Year-Old Burial Chamber's Secrets--With Drones

Teotihuacan, an ancient, abandoned city about an hour north of Mexico City, was once one of the largest cities in the world. It collapsed in the centuries ago (thanks either to an internal uprising or foreign invaders, depending on who you ask), but it's never been completely deserted, since the ruins have always been a magnet for squatters, archeologists, and hordes of tourists. More