With the Lateran Treaty of 1929, Italy recognized the full ownership by the Holy See of the Pontifical Palace of Castel Gandolfo along with the adjacent Villa del Moro and Villa Cybo, and further agreed to hand over “the Villa Barberini in Castel Gandolfo along with all of its endowments, appurtenances and dependencies” (cf. Lateran Treaty, art. 14). Sometime later Pope Pius XI wanted to make the papal residence complete with the acquisition of some orchards near Albano in order to establish a small farm.
The Pontifical Villas of Castel Gandolfo comprise about 55 hectares (11 more than Vatican City) of which 30 make up a garden while 25 are used for farming. The latter is carried out with full regard for the aesthetics proper to countryside gardening. The entire papal residence enjoys all the privileges of extraterritoriality. The properties which make up the villas include the Papal Palace (comprising also the Vatican Observatory), the Barberini Palace, apartment housing for 21 employees, an electrical plant, offices, farm buildings and animal stables. Also contained in the villas are buildings in the Villa Cybo set aside for the religious community of the Maestre Pie Filippini and their school, and two cloistered convents housing the Poor Clare and Basilian Nuns. In the piazza in front of the Papal Palace, the parish house assigned to the Salesians stands alongside the Pontifical Church of St Thomas of Villanova.
The former audience hall at Villa Cybo and the adjacent garden, which together make up about 1 hectare, were given as a gift to the Focolare Movement for its 25th anniversary.
The villas possess their own pumping station providing water from the lake for plumbing and irrigation, as well as an aqueduct that carries drinking water from the nearby springs of Palazzolo, which are also on property belonging to the Holy See.
The Administration of the Pontifical Villas oversees maintenance of the gardens, conservatories and arboretum, as well as the farming and animal husbandry conducted on the premises. It also manages the harvesting, production and sale of flowers and agricultural produce, and is responsible for the purchase and maintenance of the equipment used in all these activities. Furthermore, it handles the management of all the property belonging to the villas and ensures the efficient functioning of the water works, electrical plants, heating system and telephone system, and it oversees all other technical matters related to the villas. The Administration also manages the parking facilities for the villas and the automobile garage, along with the farm machinery. Finally, it assures that all requisite services are provided for the Holy Father during his stays at Castel Gandolfo.