The list includes ornate villas, hidden gardens, historic castles, churches, museums, and other secret spots that usually keep their doors closed.
It's part of the 'Giornate FAI di primavera' (spring days of FAI), an initiative promoted by the Italian National Trust, FAI, between March 24th and 25th. This year marks the 26th edition of the annual event, which has grown each year and offers tourists and locals alike a rare insight into Italy's hidden gems.
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The video below gives a glimpse into some of the sites on offer.
In Rome, architecture fans can head to the Neobaroque Palazzo Marini, home to the Italian Navy's central library and adorned with nautical themed sculptures, stained glass windows, and other decoration.
Milan's Pirelli skyscraper and the city's first high rise, designed by the country's top engineers and architects, will also open its doors, giving locals the rare chance to climb its 32 floors. The building houses Lombardy's regional council and visitors will be able to see both the council chamber and the panoramic views from the 31st floor.
Elsewhere in the city, curious tourists can explore the construction site of the new metro, the Gerolamo theatre which is known as 'the little Scala', and several other important palazzi and villas.
Culture fans in Florence can explore the convent of the Ognissanti, filled with beautiful frescoes, or Le Murate complex -- an artistic hub nestled in the site of a former prison. And further afield in Tuscany, visitors can head to the former mental hospital at Maggiano, a stunning 18th-century pharmacy in Asciano, or Livorno's Naval Academy.
In Sardinia, there are churches, military sites, and the Saline Conti Vecchi -- large salt plains including a natural oasis home to hundreds of flamingos, a huge natural area you can explore by train, and a museum complex -- to explore, while over 100 palazzi will be open to the public in Sicily.
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Entry to all of the sites is free, though there's an optional donation to FAI of between €2 and €5, and in a few cases entry is restricted to members of the organization. These exceptions are clearly marked on the website, where you can find a full list of the open sites across the entire country.
One example of a site only open to FAI members is the private apartments of former Neapolitan king Ferdinand II in the city's National Library, though across Naples more than 80 other cultural gems will be open throughout the weekend, including the seat of the city's chamber of commerce and Villa Rosebery on the coast, one of three official residences of the Italian President.