Northern Italy is made of the basin of the River Po, which comprises the whole of the broad plain extending from the foot of the Apennines to that of the Alps, together with the valleys and slopes on both sides of it, the Venetian Plain and the Ligurian coast. Northern Italy has the Alps as northern and western boundary and the Apennine Mountains as the southern one. In between the two mountain ranges lies a large plain made of the Venetian Plain and the valley of the Po, the largest river in Italy, which flows 652 km (405 miles) eastward from the Cottian Alps to the Adriatic Sea and receives all the waters that flow from the Apennines northwards, and all those that descend from the Alps towards the south.