The Cardinal’s house, built during the brief Borgia period in the early 16th century, is the only building in the castle specifically intended as a residence. The house was designed to provide Lucrezia or other members of the Borgia family a larger and more comfortable residence than the old Caetani home, should they visit Sermoneta. This single-storey building stands on the north-east side of the main courtyard (Piazza d’Armi) and was constructed above the cellars and stables. The house is characterised by simple architectural lines and was slightly modified in later periods. Its interior comprises seven rooms: a large reception room to the left of the central axis, and six smaller rooms — two to the left and four to the right of the main hall. Of particular interest is a mural in the first room to the right of the hall (entering on the left), showing a musical staff (from around 1580) with a brief “fugue.” The building was enriched and adorned in the first half of the 16th century by the Caetani family. The work may have been intended for the young Nicolò III Caetani, who was appointed cardinal at the age of twelve and held the title from 1537 to 1540.
