The Rive Rosse hill area, bordering on Baraggia, includes twelve municipalities between the provinces of Biella and Vercelli: Masserano, Casapinta, Mezzana, Soprana, Brusnengo, Curino, Roasio, Villa del Bosco, Sostegno, Lozzolo, Serra Valle Sesia and Gattinara.

More arid areas with low vegetation, rocky hills, ridges and gullies alternate with vineyards and small watercourses along which the vegetation is denser. There are also two reservoirs, one on the Ostola stream between Masserano and Curino, the other on the Ravasanella stream between Curino, Sostegno and Roasio.

The vegetation is characterised by herbaceous species typical of heathland: Erica Cinerea, Brugo (Calluna Vulgaris), Molinia (Molinia Arundinacea); the birdlife is particularly rich. Part of the Rive Rosse is a Site of Regional Interest (SIR). Thanks to the extensive network of hiking and cycling trails, it is a perfect area for the practice of outdoor sports, especially mountain biking.

Location: Brusnengo, Curino, Masserano, Soprana, Sostegno, Villa del Bosco, Casapinta, Mezzana Mortigliengo (Eastern Biellese and Rive Rosse)