GRIGNY, France » Paris is about to get bigger, much bigger. Next year, assuming plans move ahead, the city and a ring of inner suburbs will be joined, in an effort to redress a century’s worth of urban decisions that have exacerbated the country’s gaping cultural divide.

The new Métropole du Grand Paris, or Metropolis of Greater Paris, will include nearly 7 million people, more than triple the population now living in the central city. It will swallow rich suburbs to the west. But it should also provide better access to jobs and to business hubs and, if it really works, a greater sense of belonging for millions of immigrant families who live in poverty and isolation on the city’s southern, northern and eastern fringes. Resources would be redistributed, in particular those dealing with housing. The complexion of Paris would change.

France is scrambling to remedy the inequities highlighted by the Charlie Hebdo attack, troubles that have unraveled the nation’s social fabric and alienated Muslim and migrant youths, radicalizing a few. Urban renewal and remapping the capital are a start.

But France must also reckon with its abiding racism, which pushed poor and unwanted citizens out from central Paris in the first place. Those people came to towns like this, in the second ring of suburbs, close to Orly airport, the entry point for generations of North African immigrants who are now part of the melting pot in Grigny.

The trip here from central Paris takes an hour by commuter train, the glitter and glory of Montmartre and the Louvre giving way to the silence of a concrete railroad station below a housing project. Across a highway, a second project hunkers behind prisonlike walls: La Grande Borne, Amedy Coulibaly’s former home. Coulibaly is the terrorist who murdered a police officer in the street and then four hostages at a kosher supermarket.

One recent afternoon, the mayor of Grigny, Philippe Rio, oversaw a graduation ceremony at a community center in La Grande Borne, handing out diplomas to a dozen adults who had finished a job-training program. Unemployment nears 40 percent among young adults here; businesses in the office parks lining the highway on the other side of the wall don’t do much hiring locally. There is one small bakery to serve La Grande Borne’s 16,000 residents. The mayor cited a report showing France now spends 47 percent more on elementary school students in Paris than on those in poor suburbs like this.

"Residents of Grigny absorb exclusion into their identity," Rio told me after the ceremony. "They think they’re outsiders because that’s the way they’re treated."

As much as any struggling suburb, this one shows how urban development across decades, even centuries, has failed millions of immigrant families and contributed to what France’s prime minister, Manuel Valls, recently denounced as "territorial, social, ethnic apartheid." His remark provoked a lot of hand-wringing in France. But as all sorts of French planners, architects, historians and political scientists point out, a legacy of belonging and exclusion, center and periphery, inside and outside, is baked into the very layout of Paris and of places like Grigny, which has nice old houses and woods but is a de facto warehouse for tens of thousands of mostly poor, disenfranchised Muslims.

In essence, Paris Métropole promises a new regional council to coordinate housing, urban planning and transit for a greater Paris. The idea evolved from a proposal by Nicolas Sarkozy, who as president imagined business hubs and a high-speed train linking them to the city’s airports. That morphed into a more complex rail system serving poorer suburbs.

Pierre Mansat has spent years helping to put the plan together. He said the other morning that taxes on businesses, and, France hopes, billions more from Europe, will pay for Paris Métropole. Who knows whether right-wing and left-wing politicians from suburbs and city neighborhoods will actually collaborate, but Mansat stressed that "it’s above all about creating a new image of Paris as more inclusive, integrated, fluid."

"People in poor suburbs will belong to the same city as people in the 7th Arrondissement," he said. "This is a profound change."

Belonging is a complex issue. "Young people in Grigny have grandparents who were part of the colonial empire," said Pascal Blanchard, a social historian. "Now their parents live in the suburbs on the edge of society, in what is basically a continuation of the colonial situation, and they’re stuck there with no jobs, no hope. We keep pouring money into urban improvements, talking about new train stations and about restating French values. But the problem is skin color. And you can’t change that by changing buildings or getting everybody to sing the ‘Marseillaise.’"

Blanchard isn’t the only one who links discrimination to bricks, mortar and Paris’ urban development. The Muslim suburbs where riots erupted in 2005 once made up the medieval forest of Bondy, whose villagers Parisians at once feared and abused like serfs. When Napoleon III hired Baron Haussmann to remake the capital into a modern metropolis of boulevards and cultural palaces, Parisians from inner slums were driven out, to the edge of town.

A nowhere land, the "zone," was a military buffer beyond the wall, where the modern ring road — the immense Périphérique, completed during the 1970s — now makes a kind of concrete moat, cutting the suburbs off from the city. In Parisian potboilers from a century ago, the zone was a noirish freak show, the stinking, chaotic realm of garbage dumps, criminals, ragpickers and the sick.

Then the wall came down after the First World War, and immigrants, many of them Italian, moved into new apartment blocks built just outside the city. The zone became a suburban place of opportunity, growth. By the 1920s, its population reached 50,000. After the Second World War, that figure doubled as more waves arrived from North Africa, occupying the Grands Ensembles, immense housing projects conceived under Charles de Gaulle, among them La Grande Borne.

Designed by Émile Aillaud, with 3,600 apartments, La Grande Borne opened during the 1960s to shelter tenants evicted from proletarian districts in Paris. Aillaud consulted psychologists who said children needed trees and privacy, so he organized the complex as a low-rise ensemble of elegantly curved buildings enclosing secretive green patches. He wanted the architecture to provide variety and character.

But when the economy tanked in the 1970s, the layout became a disaster, impossible to police. Things only got worse during the 1980s. President Francois Mitterrand saw the future in cars and single-family houses that leapfrogged poor suburbs for new settlements. Residents who could still afford to leave places like the Grands Ensembles fled, abandoning them to mostly poor Muslim immigrants.

They had little say over their fate. French government is top-down. Community activism is a foreign concept. Gerrymandering goes back to the era of de Gaulle, whose right-wing government wanted nothing to do with communist mayors from immigrant suburbs. When Lionel Jospin became the country’s Socialist prime minister during the 1990s, he obliged wealthier suburbs to construct subsidized housing or pay stiff fines. Most opted for fines. After Jospin, French leaders undid employment programs and community policing initiatives that had made some headway. The mayor of Grigny, one of the few communists left, told me his town hasn’t had a full-time police station since 2002.

Parisians note that 13 percent of city residents today live below the poverty line, 20 percent in subsidized housing. Paris isn’t only a wealthy playground for tourists. But historic preservation has made it tougher to diversify neighborhoods. Officials promise 30 percent subsidized housing by 2030. Billions pour into renovating housing blocks and retrofitting barren suburban neighborhoods with streets, shops, parks and transit — but with limited results.

"It’s part of the French Republic idea that as citizens we’re all race-blind and equal," says Marie-Hélene Bacqué, a professor of sociology and urban studies at the University of Paris. "So the country even prohibits official surveys according to race or ethnicity. How can we begin to deal with problems like the poor suburbs if we won’t face basic facts?"

As Nicolas Grivel, director general of ANRU, the state agency for urban renewal, put it: "We need to change the transport system and the government of greater Paris. But we also have to do away with the psychological ring around the city."

Rio, the Grigny mayor, said he still believes that can happen: "This city and its urban development must become a laboratory for the republic." He told me he met the previous day with France’s president, Francois Hollande, and said he stressed the same thing.

"I told him we need to do better in places like Grigny," he said, "because this is a concentration of all the problems now facing France."

© 2015 The New York Times Company