Valsesia stretching from Monte Rosa to Romagnano Sesia and includes several side valleys, the waters of rivers which flow into the river Sesia.
The main valley called the Great Valley, lying in the shape of S and ends with the village of Alagna. Numerous side valleys, which are named by their respective streams, open this, the main ones are: on the left side, Val and Val Mastallone Sermenza; on the right side, Sorba Valley, the Valley Artogna, Val and Vogna Val d'Otro; height of Borgosesia on the right extends Valley Sessera.
The valley is also known as the "greenest valley in Italy." It is characterized by very high mountains and steep that do not allow a large development side of the same as in the Aosta Valley.