The Benedictine abbey dedicated to the Saints Nazzaro and Celso is surely one of the most significant abbatial complexes in north Italy. It was founded by the bishop of Novara Riprando in 1040, together with his brothers the Counts of Biandrate, who assigned it to the Benedictine monks, keeping the right of tenth for his family and himself. Situated in a strategic place, close to a Sesia river ford, it was fortified starting from the XIII century to defend itself form the bloody fights between Novara, Vercelli and Milan. The life inside the Abbey flows among an alternation of fights, lootings and truce moments until 1492, when Antonio Barbavara, a model abbot and “feudal lord” was designed abbot by pontifical bull. His regency will last for a long time: until 1567. During this period great improvements are carried out in the abbatial complex, both under the patrimonial point of view and the agricultural-communitarian organization, introducing new cultivations and reclaiming the surrounding lands. Then these are sold to privates, who, careless of the precious patrimony, adapt the rooms as agricultural depots, causing, by this way, a horrible degradation. Only about half of the XX century, thanks to the important restoration works, the abbey regained the past splendour. Of the ancient Romanesque building remain the duplex hallway with built-in narthex and the belfry. This last is a substantial square-plan building, the walls are made in river pebbles arranged in the shape of herringbone, alternated with horizontally placed bricks; the six panels are marked by a series of hanging archlets. The church, built up in the XV century, is an example of Gothic-Lombard architectural style. The saddleback façade with ogival portal and central rose-window are richly decorated with fictile frames. The interior has the nave and two aisles with cross ribbed vaults. Two 15th-century wall-painting can be admired on the right side walls. The former was commissioned by the Abbot Antonio Barbavara; it depicts the riding figure of Saint Nazzaro between Saint Catherine and Saint Rocco on the right and Saint Celso and a martyr on the left, dated 1480 it could be ascribed, after critics, to Giovanni Antonio Merli, The latter represents the Madonna with Child on the Throne, between music playing angels, inserted in an unusual architectural structure between Saint Sebastian and Saint Agata on the left. The 15th-century square-shaped cloister has big cross vaults, rich in decorations in baked clay. The very interesting cycle of contemporary wall-paintings on the cloister walls telling episodes of Saint Benedict’s life has been recently restored.