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 a big, 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.