BRUSSELS — With children’s drawings and colorful posters now adorning the walls and windows, it was easy to forget the notorious past of the red brick building, whose history still haunts a working-class Brussels neighborhood.

On a recent morning, in a former bar converted into a community center, Assetou Elabo was arranging tables for students who would soon join her for homework tutoring.

A few years earlier, the bar’s owner had let drug trafficking proliferate on the site. With patrons, he would watch videos from the Islamic State. And in the basement of the bar, Les Béguines, he would chat online with a friend who had joined the terrorist group in Syria.

Then in November 2015, he detonated his explosive vest as part of a series of attacks in and around Paris.

For many, the bar epitomized all that had gone wrong in Molenbeek, the neighborhood of nearly 100,000 people that was home to 7 of the 20 terrorists who killed 130 people in France that November and 32 more in Brussels four months later.

But if the bar symbolized what Molenbeek had been, the community center shows what the neighborhood is trying to become.

Since being opened by local residents in 2018, the center has been dedicated to helping children, students looking for jobs and people with disabilities. Although the neighborhood remains predominantly Muslim, it is more diverse than usually portrayed, with newcomers changing its composition in recent years.

“What we do here is the opposite of what the Abdeslam brothers did,” Ms. Elabo, a social worker, said of the bar’s owner, Brahim, and his brother Salah, who helped manage it.

After the Paris attacks, Molenbeek was subjected to intense global scrutiny. Television crews from around the world broadcast for days from the neighborhood’s central square or near the bar, making residents feel like they were living on a movie set.

Some journalists would stop passers-by and ask to be introduced to a jihadist. Opinion shapers and policymakers would exhort moderate Muslims to do more to combat extremism.

Six years later, many in Molenbeek have taken up the challenge. And far from the public attention, they have tried to rebuild their community, although it still faces the same endemic problems — from poverty to unemployment to crime — that contributed to the radicalization of some residents.

“We were ashamed after the attacks, but now I proudly say that I’m from Molenbeek,” said Dr. Sara Debulpaep, 47, a pediatrician who has lived here for nearly three decades.

Yet as much as some residents want to put the stigma of the attacks behind them, the Molenbeek terrorists are once again in the news.

For the past several months in Paris, a trial over the 2015 bombings and shootings has examined what went wrong in Molenbeek, presenting arguments about what drove the attackers and how their plan was allowed to so horribly succeed.

In court, academics, lawyers and officials have debated for days the upbringing of the attackers and those accused of complicity. The reasons for the failure of Brussels police officers to monitor and arrest them has been dissected even more closely.

Several defendants standing trial in Paris will also appear before a Brussels court in September for the attacks on the city in 2016.

Dozens of Molenbeek residents, mostly young people, traveled to Syria and Iraq to fight alongside armed groups like the Nusra Front and ISIS in the early 2010s. At the continuing trial in Paris, one defendant said that upon his release from prison in 2014, his neighborhood felt empty: All his friends had gone to Syria and Iraq.

Of the 20 men accused in the Paris attacks, seven grew up or lived in Molenbeek. So did one of ISIS’ top recruiters in Europe.

Luc Ysebaert, the head of the local police, said around 50 people were still being monitored by intelligence services in the area.

Since the attacks, the government has awarded numerous grants meant to improve life here and expand opportunities for the neighborhood’s young people.

Bachir Mrabet, a youth worker at Foyer, one of the main community centers in Molenbeek, said he had begun news literacy workshops after the attacks, as well as theater workshops to let off tensions. He also now organizes youth meetings twice a month instead of once every two months before the bombings. “We’re much more vigilant,” he said.

But resources are still tight, and residents still feel stigmatized, said Ali El Abbouti, another youth worker at Foyer who manages his own community center.

“We’ve been asked to do even more, to solve all the problems, but with so little resources,” Mr. El Abbouti said. “And we were already doing so much.” He wants to create places where young people are encouraged to express themselves; recent projects have included a podcast in Arabic about the origins of Molenbeek’s first generations of Moroccan immigrants.

Volunteers say young people need more guiding examples from older and successful local residents. “They want mentors, they don’t have that around them,” said Meryam Fellah, a 27-year-old chemistry student who provides coaching at the community center once housing the bar.

Molenbeek’s major changes aren’t coming only from longtime residents, but also from some of the same outside forces that are reshaping much of Brussels.

While residents of Moroccan origins remain a majority in Molenbeek, in recent years more Eastern Europeans, sub-Saharan Africans and Roma people have arrived.

The neighbors of Dr. Debulpaep, the pediatrician, include Albanians, Congolese, Guineans, Italians, Poles and Palestinians. Residents say Molenbeek’s diversity is what makes it unique.

For example, Molenbeek’s women’s soccer club last year included players from eight nationalities on one of its 12-person youth squads, said Imane El Rhifari, a coach.

Some Molenbeek residents say they are now as annoyed by the arrival of Pentecostal churches in the area as they were once worried about some mosques fostering extremism. Affluent new residents from the Dutch-speaking Flanders region of Belgium have moved into expensive housing along a gentrifying strip of artists’ studios and organic shops.

In Molenbeek, one can now visit an exhibition on Belgian adult movie theaters in one of Brussels’ trendiest museums. Art projects, underground concerts and cafes are gaining ground.

But integrating those patrons and the customers of the kebab restaurants and traditional Islamic wedding shops that dot the neighborhood’s main street remains a challenge, residents say.

“There’s very little mixing,” Mr. El Abbouti said on a recent afternoon as he walked past a gated residential complex.

And Molenbeek remains one of the poorest and most densely populated areas in Belgium. At 21 percent, the unemployment rate is three times the country’s average.

While the terrorist threat has been downgraded, cannabis trafficking has exploded, and so have violent clashes among gangs, said Mr. Ysebaert, the local police chief. “Our problems are very similar to those of large European cities.”

During the pandemic, scores of young people have dropped out of school, quit playing sports or stopped going to community centers, youth workers and residents say.

“After 16 years old, many give up, and we lose them,” said Touben Zouin, who counsels Molenbeek residents aged 16 to 25.

There have been some success stories, too. Just months after the attacks, Ibrahim Ouassari, a local entrepreneur, opened a tech school dedicated to dropouts, where 30 percent of the 400 students trained every year come from the neighborhood. The school, Molengeek, has since grown into one of Belgium’s biggest tech successes, with branches in other Belgian cities, the Netherlands and Italy.

Yet Mr. Ouassari conceded there is still a “culture of resignation” in Molenbeek which pushes some young people toward petty crime and which used to tilt some of them toward radicalization. “We haven’t dried up the fertile ground,” he said, “that creates desperate people.”