Po (anc. Padus), the largest river of Italy, rises near Monte Viso in the Cottian Alps, and, taking a N.E. course as far as Turin, then turns due E. till it discharges itself by many mouths into the Adriatic, half-way between Venice and Ravenna. Its length is about 420 miles, and the area of its basin may be put at about 27,000 square miles. It is navigable for vessels of 15-feet draught as far as the junction of the Adda, and for smaller craft to Pancalieri. In its lower reaches it has to be guarded by huge embankments, and it is liable to disastrous floods and rarer droughts. The Dora Riparia, Dora Baltea, Sesia, Ticino, Adda, Oglio, and Mincio from the N., and the Tanaro, Bormida, Trebbia, Taro, Parma, Enza, Secchia, and Panaro from the S. are its principal tributaries.