Casoli was built in the Early Middle Ages, probably founded by the inhabitants of the Roman settlement (identified by some archaeologists with Cluviae, the center of the Sannitian tribe of Carricini), whose remains are still visible in Piano Laroma.
It is mentioned (Casule) for the first time by historical sources in 878, in a manuscript listing the possessions of the Montecassino Abbey in the theatine.
The worship building is attached to the castle (perhaps it was originally the palace chapel). The church was built during the Middle Ages, it was transformed into three aisles in 1759 and, around 1820, assumed the current neoclassical structure
It stretched around a pentagonal plan view tower from the 9th century. Completed in 1455 by the Orsini, it later passed to the Aquinus princes who maintained the property until the early nineteenth century; in 1845 it was bought by the Masciantonio family who gave it to the Commune in 1981. Of the Ducal Castle is also famous D’Annunzio’s room where the famous poet was staying when he was in Casoli.
These are archaeological ruins of origin originated in the sites of Piano La Roma. He was probably subjected to by the Roman empire as he thinks of the Latin name of the site. Among the monuments to mention of Cluviae there is the theater.