Duchy of Bracciano

To gain the Medici's consent to the match, Pope Pius IV promoted Bracciano to a dukedom and added to its territories, giving the Orsini greater financial resources.

The duchy was made up of seven main lands - Bracciano, Anguillara (linked to the Orsini by personal union; technically an autonomous county, than a marquisate, ruled by the duke's eldest son), Cerveteri, Trevignano, Monterano, Campagnano and Formello, as well as twenty-five other estates, such as Palo and Viano.

[3] Vassals of the pope and the king of Spain, the various Orsini branches had accumulated a vast set of lands, reaching from the counties of Tagliacozzo (origin of the Bracciano line), Alba and Carsoli, through the viceregality of Naples and the areas around Subiaco and Lake Bracciano and ending at the Tyrrhenian Sea near castello di Palo, watching over the most important main roads into Rome.

After his death his widow Marie Anne de La Trémoille moved to Madrid, where Philip IV of Spain made her camarera mayor to queen Maria Luisa of Savoy.

The inalienable lands and ducal rank were thus transferred to the Odescalchi and very briefly to the Torlonia before finally being re-absorbed into the Papal States by Pope Innocent XII.