Anna Magnani's captivating performance in the masterpiece Rome, Open City, which is 80 this year, is a standout role that made her one of the country's finest talents.

If you asked the average person outside of Italy to name a legendary Italian actress, it's likely the answer would be Sophia Loren, not Anna Magnani. Yet Magnani is one of Italy's greatest performers. She won a best actress Oscar for her role in The Rose Tattoo (1955) – the first Italian to win the award. Marlon Brando was intimidated by her. Meryl Streep called her a "goddess". The New York Times called her "superb" and "the tigress of Italy's screen". Still, many today are unfamiliar with the "undisputed queen of Italian cinema".

Magnani is the protagonist of Roberto Rossellini's Rome, Open City (1945), a landmark in cinema history, whose 80th anniversary this year offers the chance to explore the reasons behind this apparent glitch in collective memory. Shot in January 1945, among the rubble of World War Two, the story takes place in the "long winter" of Nazi occupation, between the autumn of 1943 and the spring of 1944."Rossellini used scraps of expired film, stole power outlets from the Americans, shot in basements and locations without permits. And… he created a masterpiece," film historian Flavio De Bernardinis tells the BBC.

Inspired by the real stories of two priests executed by the Nazis, and co-written by the director, Sergio Amidei, Alberto Consiglio and a young Federico Fellini, Rome, Open City is a powerful film about the horrors of occupation and the courage of common people. "It's a political movie. Its goal was to show a good Italy – not the fascist, colonialist Italy. A country of good people," says Caterina di Capalbo, the author of a book on the film, Roma Città Aperta. At the time, Mussolini and Hitler were still alive, so when the priest in the film utters the line, "And if they come back?", he is voicing a real preoccupation shared by the film's cast and crew.

Pina (Magnani) is the moral compass of the first half of the film. She is a middle-aged widow, expecting a child by her next-door neighbour, a partisan whom she loves and plans to marry the next day. She is intelligent without having an education; poor and generous, with a clear sense of justice without being righteous. She is a woman depicted with admiration, warmth, and with a realism that is rare in cinema – then and now.

"Finally, after years of cinema where everything was fake, perfect, pretty, this was the story of a real woman, not a diva, but someone who could be anyone," says actress Olivia Magnani, Anna's granddaughter, whose godfather was Roberto Rossellini and who grew up in houses where "the Oscar was on the shelf, among letters from Bette Davis and Jean Cocteau".

Magnani was a successful 37-year-old theatre actress who hadn't been cast in lead roles in films because, as Olivia puts it, "she didn't have a tiny nose and blue eyes. She wasn't considered photogenic." Her first husband, director Goffredo Alessandrini, didn't believe she had a face for........

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