The town's name has Roman origins and derives from the name of a person "Cilius" or "Coelius", probably the name of a veteran soldier who received the assignment of these lands. It is a municipality in the province of Vercelli, whose territory is composed of several hamlets, equidistant between the Natural Park of Monte Fenera and the Natural Reserve of the Sacred Mountain of Varallo. Located in the middle of the Valsesia area, on a plateau at 685 meters above sea level, surrounded by woods, it enjoys a privileged location from where it is possible to admire the Alps, between which numerous trails can be undertaken, such as the one to Mill Benvenuto, the one to Mill Medana, the one to the village of Zagra which features typical stone fountains, the one to the village of Taira, characterized by houses and towers, and the one to the district of Merlera, the most distant from the main centre, with its unique stone houses with balconies.
The village has Roman origins. In 187 B.C. the Empire conquered the territory of Novara and reclaimed the lands that were divided between the veteran soldiers, a custom of the Romans. The funds took the names of the soldiers assignees. The first settlements, built one near to another, gave rise to several small towns. The subsequent history and the vicissitudes of Cellio are linked to those experienced by all the other towns of the Valsesia area.

Not to miss:

- the Parish church of San Lorenzo, dating from the XVI century, was enlarged in the second half of the XVII century. It features several chapels: in one, valuable frescoes are preserved and the relics of St. Cyril, in another it keeps a crucifix of excellent workmanship and frescoes by Lorenzo Peracino of 1754. In the third chapel on the left features a painting by Tanzio Varallo in which St. Charles is depicted with a cross and three glasses of 1623. Precious frescoes in the choir depicting the glorification of the Croce della Rocca (Cross of the fortress) and those of the sacristy performed by Peracino. The church has the highest bell tower in Valsesia, about 56 meters tall with 200 steps, which dominates the entire valley, with a bell of 1486, which weighs 20 tons. From the square in front of the church it is possible to enjoy a splendid view.
- the Church of San Matteo in Carega, the largest and most populous village of Cellio, presents frescoes of the artist Velatta in the choir and a bell tower made entirely of granite.
- the small Church of Our Lady of Gold built in 1686 by a shepherd in a sign of gratitude for her blind daughter, that miraculously regained her sight.
- San Jacu Pitu, an Oratory of 1400, built on the path to the Sacred Mountain of Varallo, with frescoes depicting St. James, St. Catherine and other saints.
- the church of St. Anthony, built in 1500 with several particularly valuable frescos.
- St Anne's church in Agua, located at the center of the village, contains a painting depicting the battle between the French and the troops of Valsesia of 1636
- the church entitled to Ausiliatrice in Tairano, district recognizable by the presences of houses with towers. The church houses a precious wooden gold statue depicting the Madonna
- the church of San Gottardo Valmonfredo.
- the church of San Bernardo in Merlera.
- the Civic Museum.