SPAIN: Before the Carthaginian general Hannibal crossed the Alps with his elephants, he defeated a group of Iberian tribes in a pivotal 220 B.C. battle fought somewhere along the Tagus River. Ancient writers record that Hannibal’s 25,000 soldiers overwhelmed an army of 100,000, but scholars have long argued over exactly where the clash took place. A new study using archaeological, historical, and geomorphological data has finally narrowed down the location to a stretch of river between the towns of Driebes and Illana in the province of Guadalajara.