The park downhill from the center of Atlanta has a playground, a splash pad, pavilions for parties, basketball courts, winding walking paths — and, perhaps most important to many residents, a field of open land in a neighborhood that had long been starved for green space.

But a year ago, the reason for the park’s existence revealed itself yet again: Hurricane Helene unleashed a deluge on Georgia. Much of the 16-acre park, named for Rodney Cook Sr., a longtime local politician, was submerged. The neighborhood around it was not. And that was the plan.

“I describe it as a swimming pool, the size of a football field, 28 feet deep,” said Jay Wozniak, who worked for years on the park’s design and construction as the director of the Trust for Public Land’s urban parks program in Georgia. “Nine million gallons of water — had it not been collected, it would have been filling the streets.”

50 States, 50 Fixes is a series about local solutions to environmental problems. More to come this year.

Water has always tended to collect in the low-lying bowl of an area in the Vine City neighborhood of Atlanta, just below the gleaming N.F.L. football stadium and towers that form the city’s skyline. For many years, the result of the recurring floods was swamped houses and upended lives.

But for the past four years, Cook Park has acted as a sponge during heavy rains and a gathering place for a neighborhood that needed one the rest of the time.

“It’s all woven together,” Mr. Wozniak said, “and I’d like to think it looks pretty seamless.”

As cities have been forced to adapt to a warming planet, there has been a desire to design solutions that have plenty of benefits beyond mitigating the effects of extreme weather. Cook Park is an example of creating recreational spaces that double as urban sponges, engineered wetlands and retention areas that absorb, filter and gradually release water.

In 2002, a tropical storm inundated Vine City, just west of Atlanta’s downtown, with heavy rainfall that overloaded the sewage system, sending a foul mix of raw sewage and storm water into people’s homes. After that, the government bought and razed 60 properties, with officials deciding it was unwise to allow construction on a patch so vulnerable to severe flooding.

Byron Amos, then the president of the Vine City Civic Association, said memories of the flood’s devastation made the contrast with the park today all the more astonishing.

“To be there that night, literally in the rain, to then be able to stand in the sunshine in a world-class park!” said Mr. Amos, who now serves on the Atlanta City Council.

The plan for Cook Park had been conceived in part by Park Pride, an advocacy organization in Atlanta, and the design and construction were overseen by the Trust for Public Land, a national nonprofit group. The roughly $40 million project was funded by the trust, the city’s watershed department and other donors.

The park’s design is meant to reduce flooding for a surrounding 160 acres, and limit the risk of polluting the source of Atlanta’s drinking water downstream, by using a large pond to absorb much of the runoff.

Still, for many years, the land sat empty, leaving residents relying on hope and patience.

“It took us 19 years,” said Carrie M. Salvary, a longtime resident of the neighborhood who now leads a community group dedicated to making the most of the space. “But we did it. We got this park.”

The neighborhood has taken pride in its place in Atlanta’s history. It was once considered one of the most prestigious Black neighborhoods in the city. Martin Luther King Jr. bought a house on Sunset Avenue soon after he received the Nobel Peace Prize; he and his wife, Coretta, raised their children there.

But over decades, prosperity gave way to disinvestment and decline.

Vine City came to represent a familiar problem, as neighborhoods most vulnerable to the consequences of climate change — including flooding and heat exposure — often have high levels of poverty.

But some see Cook Park as an encouraging example of what can be done to rectify that, including efforts by the Trust for Public Land, with its ambition of having every resident of American cities living within a 10-minute walk of green space. “It’s really saying we can level that playing field by investing in places and communities where there has not historically been that kind of investment,” said Carrie Besnette Hauser, the trust’s president and chief executive.

Before the park was created, Vine City had maybe a half-acre of public green space, Mr. Amos said. In some ways, he said, it is still difficult to fathom something like Cook Park existing in the neighborhood, as experience has conditioned residents to lower their expectations.

“You always hear communities of low wealth talk about the other side of town or the amenities up north or out east,” Mr. Amos said, referring to more affluent areas of the city. “This park isn’t supposed to be in downtown Atlanta.”

Still, during the planning stages, residents did not hold back on sharing their wish list for the park: Centennial Olympic Park, the green space built for the 1996 Summer Games, had a splash pad, and they wanted one, too. They also asked for playgrounds, climbing boulders, a tribute for the people whose homes had been on the land and an amphitheater.

Just about everything they asked for, the residents got — except the amphitheater, Ms. Salvary said.

She said she recognized and appreciated the protection the park provided for the neighborhood. Yet that can sometimes feel secondary.

On a recent day, balloons and gift bags had been set out for birthday parties. Children climbed around on the playground. A candidate for the school board walked around shaking hands. Ms. Salvary grumbled about a local parkour group flipping and flying around one of the sitting areas. Still, the park was bustling.

“It’s everything,” she said.