The Castle of Arienzo "Castem Vetus" which dominates Mons Argentium, known today as Monte Castello, dates back to the 7th century and was built by the Lombards to first defend the Duchy and then the Principality of Benevento. Due to its strategic position, the castle was a lookout post over the entire valley below. From 879/882, the city of Suessola was raided and destroyed by the Saracens. After the destruction of the city, following a fire, part of the Suessolani took refuge on Mount Argentarium, where there was a castle. In 1135 King Ruggero II D'Altavilla, known as the Norman, asked for it to be demolished. The latter, having to leave for Sicily, feared that in his absence the soldiers of Rainulfo could settle in the fortress and control the vast territory from above. His order was only partially carried out and later the castle was rebuilt by his son Guglielmo. From 1135, after the destruction of the Arienzo castle, the inhabitants went down to the valley where they built the new Castle of Arienzo, known as "the Terra Murata". The castles of Arpaia, Cancello, Maddaloni, Casertavecchia were built on the highest peaks of the surrounding mountains.