IN ANCIENT TIMES, FUCINE LAKE in Abruzzo, Central Italy, was a large endorheic lake with no natural outflow. The lake provided fish and fertile soil but was also the source of malaria and frequently flooded, so the Romans tried to drain the entire basin.

To accomplish this ambitious goal, Roman Emperor Claudius commissioned the construction of a system of canals, tunnels, and wells between 41 and 52 CE. Over 30,000 slaves and workmen are believed to have manually dug the tunnel system.