The Castle of Montesarchio is one of the best examples of military architecture in Campania and stands on the town’s hill, an area on which the walls and tower were also built, a defensive element made from the limestone of Mount Taburno.

Erected in the 8th century by the Lombards, it was destroyed by the Normans and rebuilt in the 15th century. Although the primitive building has been almost completely altered, some traces of the original work remain in the basement of large square blocks in parallel rows and in the gaping openings at the foot of the masonry. Formerly used as a prison, it is now home to the National Archaeological Museum of Sannio Caudino.