SAN FRANCISCO — Two years ago, United Nations Plaza was vying for the title of “Saddest Place in San Francisco.” A sunny brick promenade surrounded by government buildings, the plaza had become a trash-strewn dumping ground for the city’s most vexing problems.

A typical weekday scene might have included a team of paramedics reviving a limp teenager overdosing on fentanyl, against a backdrop of merchants selling stolen cellphones and a fountain being repurposed as a toilet.

For a city struggling to recover after the COVID-19 pandemic, the images of suffering and bedlam could not have been more inconveniently placed: U.N. Plaza, a block from City Hall, has a busy rail station and is bordered by Market Street, a major thoroughfare that double-decker tour buses cruise daily. In 2023, after an international conference announced that it was coming to the hobbled city, the parks department scrambled to find a new life for the site.

That turned out to be a skateboard park. On a recent sunny morning, kids in baggy pants slid the railings around a flagpole and cruised over a volcano-shaped embankment. The old granite ledges that used to be illegal to skate on were now open to grind and slide.

Inviting a bunch of skaters to rip around, scuffing ledges, is not the use San Francisco had in mind in 1975 when the plaza was dedicated to commemorate the founding of the United Nations in the city. U.N. Plaza was part of a larger redevelopment meant to attract affluent shoppers to San Francisco from the suburbs. Instead, for the next four decades, the city produced regular reports of failure that highlighted assaults and drug use on the plaza and high vacancies in the buildings surrounding it. For all the thought that went into the open design and gushing fountain, it was never clear what people were supposed to do there.

A defining feature of the new skate park (or skate plaza, the name the city and skaters prefer) is that it’s a retreat from the grandeur that characterized earlier efforts. It also seems to be working better, with a $2 million price tag and just a few months of planning, than the catalog of failed projects, costing hundreds of millions, that preceded it.

Nobody is saying the plaza’s makeover has solved the deep, systemic problems that made the area a hub for addicts and homeless people. The dealers who previously congregated there have migrated to a spot near the very next train stop.

What the transformation of U.N. Plaza does show, however, is that attempts at urban revival can go a long way for relatively little money when they attract a natural constituency of users. Obvious as that may sound, it’s the opposite of how planners in San Francisco and elsewhere have historically operated. The notion that a great public space is defined by architecture first, people second, was so ingrained in the city’s thinking that it took the squalor brought on by the pandemic to reverse it.

“U.N. Plaza was created with all these wrongheaded urban planning ideas of the 1960s, that you need grand plazas and grand connectors, which works great for eight parades a year and kind of fails otherwise,” said John King, an author and a former architecture critic for the San Francisco Chronicle.

“The smart thing here,” he added, “was the city realizing that a good way to get people somewhere is to create a looser space where certain types of people just want to be, in this case skateboarders.”

An Easy-to-Please Constituency

I should probably acknowledge that I grew up in and around San Francisco and have been skateboarding since I was 10 in the late ‘80s. But I’m not being a homer when I say that while Los Angeles is the cradle of the sport, San Francisco has long had an outsize role in skateboard culture.

It’s the home of Thrasher Magazine, for starters. And unlike their peers in suburban Southern California, where a typical day of skateboarding can include two hours of driving between spots, San Francisco skaters use the city as a skate park, “bombing” hills in traffic and honing their tricks in downtown squares alongside office workers eating their salads.

Until recently, the city’s default position was that skaters who showed up in its plazas were a nuisance to be removed. Most of the time this played out as a cordial cat-and-mouse game in which the city and building owners shooed skaters away, knowing they’d be back later.

Occasionally it got aggressive, with police issuing tickets, confiscating boards and removing the obstacles skaters are attracted to.Market Street used to be lined with black granite benches whose hard, smooth edges are a perfect surface to grind. The benches become so popular for skateboarding that the city hauled them off to a municipal yard where no one could use them.

The Police Department’s approach to illegal skateboarding has lightened up in recent years as homelessness and open drug use have eclipsed everything else. After the pandemic and remote work hollowed out downtown San Francisco, the city realized that skaters might offer a way to bring people back.

“Healthy activities give people a reason to congregate for positive reasons rather than congregating for, you know, bleaker reasons,” said Phil Ginsburg, general manager of the Recreation and Park Department.

Today the city and the local skate community have what you might call a working relationship. Anytime the parks department considers adding legal skateboarding to a new space, Ginsburg said, he calls a handful of skaters for advice. One thing he has learned, he said, is that skateboarders do not need much to be happy.

Consider a 2022 project to put a small skate park on a barren stretch of asphalt on Waller Street at the edge of Golden Gate Park. The strip had long been a pop-up skate spot with a few small obstacles and a makeshift ramp. The city wanted to lean into the identity and asked what it could do to help.

The answer, said Ashley Rehfeld, a local skater who works as a marketing strategist in the skate industry, was to outfit the park with the granite benches that the city had yanked from Market Street.

“And the city was like, ‘Wait, that’s all that needs to happen?’” Rehfeld said in an interview.

So one day, at the city’s invitation, she and a small group of skaters drove to the yard and walked around spray-painting X’s on the pieces they wanted. The city loaded them up on a truck and used a crane to install them at the skaters’ direction. Including a resurfacing of the street, the total cost of renovation came to $218,000 — an impressively low figure in a city that once put a $1.7 million price tag on a single public toilet.

Another thing that Ginsburg said he had learned from working with skateboarders is that they operate as the informal “watchful eyes” that urbanist Jane Jacobs described as a crucial element of safe streets. They cover a lot of space, they watch out for one another, and unlike a concert or special event, skaters require no special programming from the city. They just show up in short bursts throughout the day, helping to maintain activity outside working hours.

This, as it happened, was precisely the mix of attributes the city was looking to create at U.N. Plaza.

One of the biggest advantages was the putrid state of the park, which made it hard to argue that the status quo was preferable.

U.N. Plaza is not some epic skate park; it’s just a bunch of ledges along with a rail and a few small embankments. If you’re a skater, it’s a fun place to pass through for an hour or less. The most popular features seem to be the granite ledges that have been there for decades and a long low curb that looks as if it had been transported from a Costco parking lot.

Most of the people in the plaza do not come for the skateboarding. People drink coffee at bistro tables and take outdoor exercise classes and play table tennis at concrete platforms added with the renovation. On a recent afternoon as I stood in the plaza with Ginsburg, he interrupted his narration of the park’s odyssey to proudly point out the perfectly ordinary sight of a pedestrian crossing it from a nearby building to the train station. Commuters, he said, used to take the long way around.

“They would never walk through here before,” he said. “Ever.”