The history of Cesi is closely linked to the birth and development of the Terre Arnolfe, a fortified territory that included many villages and which had Cesi as its main centre
According to tradition, the foundation of Cesi took place after the "ruin of Carsulae", when the inhabitants took refuge in nearby Casventum and at Cesi. However, there are no documents that can confirm this theory.
After 962, Emperor Ottone of Saxony enfeoffed the area of Terre Arnolfe and entrusted it to one of his advisors called Arnolfo. This event marked the beginning of the history of Terre Arnolfe, of which Cesi became the main centre.
The Fortress of Cesi, located on the mountain of St.Erasmo, was seat of the castellan or governor who, nominated by the Pope, had the jurisdiction over all the Arnolfe lands. Cesi’s strategic role was so important that it was disputed by Terni, Todi and Spoleto.
Cesi reached its peak during the 16th and 17th centuries. Despite the struggles between the Papacy and the Empire, it remained under the control of the Papal State and continued its role of "capital" of the Terre Arnolfe until the early 18th century.
In 1525, Pope Clement VII assigned the lordship of Cesi to Paolo Cesi of Acquasparta, who commissioned the beautiful building that can still be admired today in the historical centre. Other noble buildings rose up in the same period.
In 1861, the first municipal council of Cesi was formed, but in 1927, the municipal territory of Cesi became part of the Municipality of Terni, a town which was elevated to provincial capital in that year.
