There is more than one answer, but one is paramount: In Milan, political opponents work together, and business and cultural institutions tend to join forces for the common good. They think glory and wealth can be shared, if things get done. This belief has been the city’s hallmark for 20 years, and now, despite the infighting and the impotence of the national government, it is producing results.

The Milanesi are individualists, like most Italians. But they can play as a team, and win matches.

In Rome, by contrast, the anti-establishment Five Star Movement and the right-wing League, after winning the 2018 election, formed an awkward coalition based on a “government contract” that is irritatingly vague on everything important. Prime minister Giuseppe Conte’s full-time job is to settle arguments between his deputies, Matteo Salvini, the larger-than-life maverick interior minister from Milan who led the League to a big success in the recent European election, and the inexperienced, clean-shaven Luigi Di Maio, a Five Star populist from Naples who was unwisely picked to run the labor and economic development department, and seems overwhelmed by the task.

The two men disagree on everything: immigration and regional autonomy, the minimum wage and tax reform, the steel industry and new railroads, defense and vaccination. This has brought Italy to a standstill, and may bring a general election soon.

Milan, 360 miles and three hours of high-speed train to the north of Rome, inhabits a different political planet. Mayor Giuseppe Sala, from the Democratic Party, and Lombardy’s governor, Attilio Fontana, representing the League, work well together. They teamed up with Luca Zaia — the governor of Veneto, also from the League — to bring the Winter Olympics to Northern Italy.

And in Milan, cooperation goes beyond institutions. The Milanesi are determined to work with whichever officials are elected. The city’s previous right-wing mayors — Gabriele Albertini and Letizia Moratti, both elected with Silvio Berlusconi’s support — have not been boycotted by Milan’s liberal intelligentsia. Instead, successive left-wing mayors, first Giuliano Pisapia and now Mr. Sala, worked well with the business community.

Why’s that? The corruption scandals and investigations in the early 1990s, labeled “Mani Pulite” (Clean Hands), turned out to be a healthy wake-up call. In addition, Milan and Lombardy account for 22 percent of the country’s gross domestic product and are among the richest areas in the European Union. And Milan is where many of Italy’s pivotal changes of the last century — good and bad — started: Fascism in 1919; resistance to Fascism in the 1940s; the economic boom of the 1960s; political turmoil in the 1970s; the rise of a modern socialism and the populist Northern League in the 1980s; and the narcissistic politics of Mr. Berlusconi in the mid-1990s (20 years before Donald Trump!).

This century, at last, has brought cooperation and bipartisanship, and they have transformed the city — its look, its mood, its livelihood.