The sign on the Largo Goldoni at the foot of Rome's posh, extravagant Via Condotti -- the fabled showcase of such barons of the Italian style as Bulgari, Gucci and Ferragamo -- is simple but unmistakable.

Put up just a week ago, the two gold arches on a red background announce that, 450 yards up the street of posh shops, at the Piazza di Spagna -- of the sweeping marble stairs and Bernini fountain that cools so many summer tourists' feet -- an American revolution has begun in the land of pasta.

After years of trying to break into the tradition-bound Italian food market, the all-American, mass-produced hamburger has arrived. Long a staple in such world capitals as London, Paris, Tokyo and Hong Kong, McDonald's finally is opening its first hamburger haven in the Eternal City of popes and Baroque palazzi.

"I think the market here is over-ripe for a McDonald's," said Jacques Bahbout, the Egyptian-born Frenchman who hopes to be pushing quarter-pounders over the counter by Thursday. He is making a McDonald's out of a former sandwich and coffee bar named Rugantino's, which he owned. "It is time to modernize the food business here," he said.

Bahbout, who worked for the United Nation's Food and Agriculture Organization until he "decided to get rich" and invested in supermarkets and small restaurants, said he is aiming his McDonald's food line at the "millions of people who go shopping around the Piazza di Spagna and have no place to sit down."

Bahbout said this McDonald's is going to be the biggest ever among the 9,006 that the fast food chain has franchised around the world -- 500 of them in Europe alone. When the remodelling of Rugantino's is completed this week in time for a gala opening for the press and local dignitaries, there will be seating for 450 in the second-floor dining room that will be approached through a ground-floor entry made to look like an Italian village street complete with cobblestones.

"Let's say it is McDonald's plus," Bahbout said, emphasizing that the typical McDonald's burgers, fries and colas will be sold but that he will hold the Egg McMuffins because he doesn't think Italians are ready for such an innovation.

He will, however, offer McDonald's latest innovation with "16 linear meters" of salad bar and will have a piano and pianist in the dining room.

Bahbout's plans to set up his American fast-food parlor in the heart of Rome, amidst such traditional local trattorie as Nino's and Da Mario's, has caused hardly a ripple of concern in the centuries-old neighborhood that in the past two decades has blossomed into the Fifth Avenue of the eternal city.

"I can't complain," said Pasquale, the bustling, beaming waiter who is one of the pillars of Nino's, regarded by cognocenti as the most serious restaurant around the Piazza di Spagna. "It is certainly something different, but the people who will eat there are not the people who eat here. So I don't see any problem."

The lack of shock at McDonald's setting up shop in the shadow of the towering statue of the Virgin Mary where popes traditionally lay wreaths on the anniversary of the Immaculate Conception, is explained by the fact that its traditional giant-arches trademark will not grace its entrance. The facade will blend in with the rest of the 17th century buildings that line the famed cobblestoned piazza.

Fast food is not altogether that much of a novelty in Italy. Restaurant critic Federico Umberto D'Amato of the prestigious "Guida d'Italia" maintains that Italy probably invented fast food with street foods such as Neapolitan pizza and precooked dishes normally served at traditional "tavola caldas," or snack bars.

"Italy has had its fast foods for centuries," D'Amato said in an interview. "Every region in Italy has its own varieties because, despite the popular image, many Italians don't go home for big sit-down lunches of pasta and wine but eat light lunches off the streets.

"There is much more variety to our fast food than is to be found in McDonald's hamburgers," D'Amato said. "That is why I think this is a fad that will soon pass when the novelty wears off about having a real American McDonald's in Italy."

That is something Bahbout is betting against. He hopes to have two other McDonald's operating before the end of the year.

Various fast-food parlors, with names such as Boburg, Benny Burger and Big Burg beat McDonald's to the punch in Rome. But the arrival of McDonald's is seen as the final assault of American fast food in the land of fettucine and lasagna. No one doubts that after the Big Mac such other un-Italian food innovations as Kentucky Fried Chicken cannot be far behind.