The patron saint of Guidonia Montecelio is Our Lady of Loreto: the feast day falls on 10 December, but the feast is celebrated on the third Sunday of September. The church of Santa Maria di Loreto, built in 1938 to a design by Giorgio Calza Bini together with the entire urban plan for the new town of Guidonia, stands on a hill in a dominant position, almost like a sanctuary: in the designers' intentions it was meant to be the centre of future residential growth, following the tradition of Italian towns that grew up around a religious hub. Each hamlet of the municipality also has its own patron saint tied to its own parish.
The municipality was born in 1937 from the merger of the old municipality of Montecelio with the new Fascist-founded town of Guidonia, which arose around the military airfield named after Alfredo Barbieri: the airfield, built during the First World War as a pilot training centre, became after the conflict a base for experimental and aeronautical research activities, laying the groundwork for the development of the hub that would give rise to the town. The very name Guidonia recalls Alessandro Guidoni, an Air Force general who died tragically on 27 April 1928 during a parachute-drop test near what was then the Montecelio airfield.
