The question of precisely where the historically acclaimed general Hannibal and his army crossed the Alps into Italy to defeat the Romans — during the Second Punic War, around 218 to 201 B.C. — has perplexed historians for nearly 2,000 years. Thanks to a new study, the first evidence pointing to an answer has finally been unearthed. Clues to Hannibal’s secret military route were recently discovered — not in maps or letters, but in the geologic record. But it wasn’t exactly rocks that revealed the full story. Scientists dug up signs of Hannibal’s passage in preserved poop deposits, from a churned-up stretch of boggy terrain that likely served as a watering hole and toilet for the army’s resting animals.