The origins of the town's name are uncertain: for some historians it derives from the Latin "V legio" (fifth legion), for others the composition of the two words "ol "and" esin "(hill of the river Ticino), while another group of thought contends, however, the origin from "ulivetum" (olive).
It is a municipality in the province of Novara, located halfway between the city of Novara and Lake Maggiore, on a hill from which it is possible to admire a unique panorama of the surrounding plain. To the East, in a location where the terrain is particularly steep in the Middle Ages a series of ramparts were built. The local economy is mainly devoted to agriculture and particularly the cultivation of vines and cattle farming. The town is also famous for an important Carnival parade that takes place each year for the last sixty years.
The area was at first inhabited by tribes of Celt-Ligurian origins, which were defeated by the Romans, who settled in these places and whose presence is evidenced not only by the characteristic structure of the settlement, but also by the discovery of numerous findings of the time. With the fall of the Roman Empire and the consequent state of disorder and insecurity that followed, the town submitted the continuous raids of Lombards, Magyars and Saracens. After several attacks and looting the local inhabitants built a castle, whose remains are still visible today. Later the territories submitted the domain of the Counts of Biandrate, of those of Novara and of the Visconti and then, under the Sforza, the town became independent from Novara. From the second half of the XV to the XIX century it was under the jurisdiction of the Count Bolognino. In the XVI century the town was occupied by the Spanish and during the Thirty Years' War and the War of Monferrato, due to its location, it was directly involved in the conflict. Finally submitted to the Savoy, except for a short parentheses in the XIX century.

Not to miss:
- the Shrine of the Assumption in Loreto, built between the XVI and the XVII centuries, incorporating an existing chapel, within which there is a fresco depicting the Madonna of Loreto;
- the Church of the Annunciation, built in the second half of the XVII century, it houses five altars, the largest of which is enriched by an altarpiece depicting the Annunciation;
- the Parish Church of Saints Peter and Paul, from the second half of the XIX century, built in the highest point of the town, on the remains of a smaller pre-existing church. It is in neo-Classical style, preceded by porch and gable, with three naves and apses. Inside it preserves a painting of the Immaculate Conception of Mazzucchelli and an altarpiece of the artist Lanino;
- the Church of San Michele, already documented since year 1000, feature a façade divided by pilasters and has three aisles, in Romanesque style with three apses. Inside are preserved particularly valuable frescoes;
- the Oratory of Santa Maria in Galnago rebuilt in XIV century, it features a single nave ending in an apse that dates back to an earlier period, probably XIII century. Inside it preserves frescoes of the XV and XVI centuries;
- the Oratory of the Nativity of St. Maria in Gaggiolo, in Romanesque style with exquisite frescoes inside;
- the XVII century Oratory of the Holy Cross;
- the Oratory of SS. Name of Jesus;
- the Oratory of St. Christopher;
- the Oratory of San Donato;
- Palazzo Bellini, renovated in the late XVIII century, in neo-Classical style, decorated with stucco and paintings from the XVIII and XIX centuries;
- the Bell Tower, once part of the castle, today presents itself as the result of several subsequent renovations. The foundations probably date back to Roman times, while the central part is in Romanesque style and the belfry, which was added in 1840.