Still today, it is considered one of the greatest military feats ever. In 218 BC, a Carthaginian army of ninety thousand men and three dozen elephants set out to cross the Alps to challenge the might of Rome. The exact route chosen by Hannibal, its charismatic commander, has been a matter of dispute ever since. Now, researchers believe they might be able to track his route. Their evidence — horse manure. They believe that Hannibal opted for the Col de la Traversette, until now regarded as the most unlikely option. According to geomorphologist William Mahaney, “It’s only from here that he could have overlooked the Po Basin,” as is related by ancient sources. In summer 2017, Mahaney and microbiologist Chris Allen took soil samples on the Italian side, and they are hoping that the lab results will further back their hypothesis.