Po River, a river in northern Italy. It is 418 miles (673 km) long—the longest in the nation—and is navigable for most of its length. The Po begins on the eastern slope of Monte Viso, a few miles east of the French border. It flows east and north to Turin, then eastward across the Plain of Lombardy, emptying into the Adriatic Sea 31 miles (50 km) south of Venice. The Po Valley, irrigated by the river's waters, is the broadest and most fertile in Italy.
The Po was called the Padus by the ancient Romans, who began the first irrigation and reclamation works. Major cities along the river are Turin, Piacenza, and Cremona.