It served for centuries as a summer residence and vacation retreat for the pope, the leader of the Catholic Church, and is afforded extraterritorial status as one of the properties of the Holy See.

Since then, about half of his successors have used the properties as a summer residence and vacation retreat,[3] except for the years between 1870 and 1929 when the popes, in dispute with Italy over territorial claims, did not leave Vatican City.

[4] In accordance with the Lateran Treaty of 1929, the palace and the adjoining Villa Barberini added to the complex by Pope Pius XI are extraterritorial properties of the Holy See.

[16] When asked if the building would again become a papal apartment, Castel Gandolfo mayor Milvia Monachesi said: "the fact that the palace is now a museum will make a reversal in the future difficult".

[17]Pursuant to the Lateran Treaty of 1929, the Papal Palace of Castel Gandolfo is Italian territory, but owned by the Holy See and equipped with extraterritoriality comparable to that of diplomatic missions.