Italy is a mountainous country, with the Alps as the northern boundary and the Apennine Mountains forming the backbone of the peninsula, but in between the two lies a large plain in the valley of the Po, the largest river in Italy, which flows 652 km (405 mi) eastward from the Cottian Alps to the Adriatic. Worldwide-known mountains in Italy are Matterhorn (Cervino), Monte Rosa, Gran Paradiso in the West Alps, and Bernina, Stelvio and Dolomites along the eastern side of the Alps.