The sites include rarely-opened palaces, castles, abbeys, libraries, parks, nature trails and gardens in around 300 towns and cities across the country, with the FAI identifying some of the highlights on this year’s itinerary:

Rome: the usually inaccessible 17th-century Villa del Vascello, home of the Grande Oriente d’Italia, the oldest Masonic institution in Italy.

Turin: the recently refurbished apartment of Carlo Felice di Savoia at Palazzo Chiablese, a wing of the Royal Palace of Turin.

Bologna: the 16th-century Palazzo Caprara bought by Napoleon for his granddaughter Josephine of Leuchtenberg, Princess of Bologna and later Queen of Sweden and Norway.

Genoa: the Mackenzie Castle, an eclectic city manor in Renaissance and neo-Gothic style built at the end of the 19th century by the then-unknown architect Gino Coppedè.

Naples: the Pausilypon Archaeological Park which overlooks the sea and is reached through the Roman tunnel called Grotta di Seiano, an area rich in ancient Roman ruins.

Reggello: the Sammezzano Castle, 40 kilometres south of Florence, a kaleidoscopic triumph of Moorish Revival architecture, closed to the public for decades.

The FAI works to preserve and promote Italy’s cultural heritage through education, restoration and annual open days.

Since it began in 1993, the spring open day initiative has attracted about 11 million visitors.

The event usually takes place in March, but was postponed this year due to COVID-19 restrictions.

It was cancelled altogether last year amid Italy’s strict lockdown.

The regions of Sicily, Sardinia and Valle d’Aosta will be excluded from the 2021 initiative, as they are still designated moderate-risk “orange zones” due to higher infection rates.

The complete list of participating buildings and monuments can be seen on the FAI website.