Fourth edition of Open House Roma features 170 guided tours and 70 events.

Many of Rome’s museums, libraries, galleries and contemporary buildings to which there is normally limited public access are open free of charge over the weekend of 9-10 May as part of the fourth edition of Open House Roma.

Since its launch in 2012, the annual initiative dedicated to Rome's varied architectural design has opened the doors of more than 300 interesting, important and sometimes off-limits buildings.

This year the two-day programme features 170 guided tours and 70 special events (including children's activities) in public and private venues all over the capital, from the centre to the suburbs. The event sees the city sub-divided into seven areas: historic centre, Flaminio-Parioli, Nomentano-Pietralata, Esquilino-S. Lorenzo, Appio-S. Giovanni, EUR-Corviale, and Monterverde-Ostiense.

Visitors can enjoy a behind-the-scenes peek at an eclectic list of participating buildings including the Hertziana Library near the Spanish Steps; the Palazzetto Bianco off Via Gregorio VII; the senate buildings at Palazzo Madama; the Mario Praz Museum near Piazza Navona; the Nuvola Centro Congressi EUR, better known as the Nuvola, by architect Massimiliano Fuskas.

There is a tour around the churches of the Aventine hill; street art among the apartment blocks of S. Basilio; Teatro Argentina; Villa Farnesina; the Corviale flat complex; even tours on the number 19 tram from Verano to Centocelle.

However it is the lesser-known venues that are perhaps the most exciting, such as architectural studios, cutting-edge private apartments and even construction sites.

International institutes participating this year include the Spanish Academy, the Brazilian embassy, the American Academy, Casa di Goethe, the French Academy at Villa Medici, the Danish Academy, the Japanese Cultural Institute, and the residence of Germany's ambassador to the Holy See.

Co-ordinated by non-profit cultural association Open City Roma and its more than 400 volunteers, there are 70,000 visitors predicted at the 2015 event, an increase of 20,000 compared to last year.

On 3-4 October, Milan will become the second Italian city involved in the worldwide initiative which began in London in 1992.

Booking is required for many of the Rome tours, some of which take place on Saturday only or Sunday only – for full details see website or check out Open House Roma Facebook page.