By RACHEL DONADIO

ROME-On a crisp Sunday morning in January a powder-blue Alfa Romeo roadster pulled into Piazza del Popolo with Daniel Day-Lewis at the wheel and Sophia Loren in the passenger seat. He wore sunglasses. She had a large diamond cross plunged into her decolletage. Both smiled knowingly. An Italian question came to mind: Were they lovers? Or mother and son?

It turned out that Mr. Day-Lewis was playing Guido Contini, the blocked film director at the center of “Nine,” Rob Marshall’s film based on the Broadway musical “Nine,” in turn based on Fellini’s “8?.” And Ms. Loren was indeed playing his mother - or a vision of his late mother - in one of the many dream sequences in the film, which opens widely in the United States on Christmas and around the world in January and February.

Ms. Loren is far from the only leading lady comforting or bedeviling Mr. Day-Lewis’s Guido in the film. Beyond the Mother, the film includes other Italian archetypes: the Wife (a soulful Marion Cotillard); the Mistress (a smoldering Penelope Cruz); the Whore (an unbound Fergie); the Muse (a goddesslike Nicole Kidman); and lesser-known members of the Italian pantheon: the Confidante (a matronly Judi Dench) and the Journalist (a perky Kate Hudson).

So what was it like working with that sort of cast? “Where do you begin?” Mr. Day-Lewis said, laughing . “It was just pure pleasure to be there every day.” As for his drive in the roadster, “I told my mom about it the evening after the scene, and she was absolutely enthralled when I told her Sophia was playing my mom,” he said. “I can’t think of anything that excited her more since I started working.”

In “Nine” Guido’s film is called “Italia,” about Italy as “a myth, a woman, a dream,” as he puts it. Filming “Nine” gave everyone a chance to live out fantasies of the Dolce Vita era. Mr. Marshall, whose 2002 film version of the Broadway musical “Chicago” won six Oscars, said he was drawn to the period’s look. “It was so chic and such a great time,” Mr. Marshall, 49, said on the set in January at the historic Cinecitta film production hub here. “People dressed for dinner. I was born a little too late.”

The production, filmed mostly at Shepperton Studios outside London, spent a month in Italy. At Cinecitta they were able to use Studio No. 5, where Fellini used to work. “I would have shot the whole thing there,” Mr. Marshall said in a recent telephone interview. But “it was a question of dollars and cents.” Production and labor costs are very high in Italy, and Cinecitta is not thriving. “It was a little disappointing to see we were the only film there,” he said. “My great hope is that film can return there.”

In spite of the hassles, nothing quite compares to Italy, he added. Mr. Marshall said he, Mr. Day-Lewis and others involved in the production traveled there before starting filming in England. “We needed to feel it,” he said. “It’s a different feeling. There’s a freedom and a joy. It’s about food, clothing, style. It’s about life. That’s why I love Italy.”

In “Nine,” as in “Chicago,” Mr. Marshall’s challenge was to make stage numbers (from the 1982 musical by Arthur Kopit, from the Italian by Mario Fratti, with music and lyrics by Maury Yeston) work on screen. He chose to use dream sequences and flashbacks for songand- dance numbers in the “Cabaret” vein. “The numbers were fantasies in his mind, and conceptually I chose to place all of them on the unfinished set of his soundstage,” Mr. Marshall said. “I find there are no limits in film, so I try to place limitations on myself.”

As in Fellini’s “8 1/2,” “Nine” is about a director struggling to come up with an idea for his still scriptless film, who escapes to a spa to take the waters and get away from producers nagging him about money, actresses complaining about the size of their roles and journalists asking banal, irritating questions.

The spa scenes were filmed in Anzio at the same former casino Fellini used in “Amarcord” (1973). Mr. Marshall said he didn’t know the site’s history until he started shooting. When he learned, “it felt like kismet,” he said.

Once you get past the idea that “Nine” has put in Technicolor song and dance everything that Fellini’s perfect 1963 film left unsaid or narrated in lush shades of gray, the movie is a feast for the eyes, highly stylized like a period television show. “Style is the new content,” Ms. Hudson, playing a journalist for Vogue, tells Guido.

Famous for his total immersion into his roles (a technique that won him Oscars for “There Will Be Blood” and “My Left Foot”), Mr. Day-Lewis is not the first actor who comes to mind for a musical.

To prepare for the role, Mr. Day- Lewis said, he watched all classic Italian cinema of the golden era - Pietro Germi’s “Divorce Italian Style” (1961) is a favorite - but appearing in a musical had other challenges.

“Singing, for instance,” Mr. Day- Lewis said with a laugh. So would he do it again? “I don’t know,” he said. “I don’t know if I’d take the risk more than once.”

As for Mr. Marshall, he seemed ready to shoot the whole film over again. That winter morning, “I said, ‘Action,’ and I couldn’t quite believe we were there, that I was actually in Rome shooting with Sophia Loren in Piazza del Popolo in front of a cafe,” Mr. Marshall said. “I could have died and gone to heaven.”

Kate Hudson, center, and other dancers in ‘‘Nine,’’ a film based on the Broadway musical. / DAVID JAMES/THE WEINSTEIN COMPANY