One of the most desirable features of antique furniture is the patina that comes with age — so much so that an aggressive refinishing job will often diminish the market value of a piece. Dirt and grime aren’t as glamorous, however, when the antique in question is a prominent work of public, outdoor art. That’s why the area around Grant’s Tomb in Morningside Heights is once again home to hundreds of busy volunteers as they restore “The Rolling Bench,” a 35-year-old, multicolor mosaic sculpture that was beginning to show its age.

The sculpture is a series of 17 benches surrounding the neoclassical tomb of Ulysses S. Grant at 122nd Street and Riverside Drive. When the project, the brainchild of artist Pedro Silva, was finished in the early 1970s, it stood as the largest public art project in the nation’s history.

Although “The Rolling Bench” was designed by Mr. Silva and sponsored by the nonprofit City Arts organization, it was built — just as it’s being restored today — by children from the surrounding neighborhood. “There’s nothing better than when youths are doing something responsible for their community,” the executive and artistic director of City Arts, Tsipi Ben-Haim, said. “This is about community identity.”

City Arts, founded in 1968, aims to bring urban children together with professional artists. Over the past four decades, the group has overseen hundreds of local projects that address civic and social issues. Ms. Ben-Haim said that the Grant’s Tomb restoration project is important because it’s one of City Arts’ most recognizable works.

“I strongly believe that as kids create, they do not destroy,” Ms. Ben-Haim said. “The reaction of the children is amazing to watch. ‘What if we’re caught?’ was the question they always ask me. I tell them that they’re being asked to restore these benches and that they’re being given an opportunity to show they care.”

Sons and daughters of the children who built the benches are part of the current team. So are some of the six young artists who helped Mr. Silva build the structure on which the mosaics were installed. Don Shanley was a 21-year-old student at the School of Visual Arts who spent the summer of 1972 mixing concrete and forming the rebar. “The project got lots of people together who wouldn’t have otherwise gotten together in those days,” Mr. Shanley said. Today, he is an artist, and he recently helped with another public art project: Christo and Jeanne-Claude’s “Gates” in Central Park in 2005.

Mr. Silva, now 73, is directing the restoration with his son, Tony, who was a 10-year-old when the installation was first built. The elder Mr. Silva envisioned that the benches surrounding the tomb would each tackle an issue facing the children in their neighborhoods. They were a prescient and sophisticated bunch: Global warming is one of the issues they chose to address in the mosaic work back in 1972.

Mr. Silva also correctly assumed that he should leave space between the benches for the London Plane trees circling Grant’s Tomb. Over three decades, the trees have each reached heights of nearly 100 feet. “In the next 30 years, they might start pushing the benches up from the ground,” Mr. Silva said.

The overall theme of the project is “Man and His Environment,” according to Mr. Silva. One section, for example, is devoted to the world’s oceans and shows a wide range of aquatic life, including an octopus and squid fighting. For such a scene, Mr. Silva had concrete poured around galvanized rebar, which gives the benches their sculptural look.

Wire mesh went over the concrete and serves as a solid base for the mortar and cement that hold the mosaic tiles in place. Mr. Silva and his son use the same production line methods they used in the summer of 1972: A group of eight to 10 children work around each section of the bench. They cut the tiles to fit a pattern created by Mr. Silva.

When they’re ready, they cement the tiles in place and then spread layers of mortar to seal the entire pattern. This time around, of course, much of the restoration work involves pulling out loose tiles and matching colors with a new batch. Mr. Silva said that among the most popular benches are the ones depicting a taxi and the city skyline, as well as the medieval bench and the writers-philosophers bench.

Jordan Taler, a recent graduate of Skidmore College who wrote his senior thesis on public art, is the creative director at City Arts, and oversees the teams of volunteers. He’s become accustomed to working with anyone who shows up to work — from investment bankers at Lehman Brothers to 12-year-olds from Harlem. There’s even interest from visiting foreign students and tourists, he said.

“Some of the kids today have brief attention spans, and some come here and start looking for cans of spray paint. It’s all about immediate gratification for them. But then we teach them about mixing cement and applying grout and their interest begins to take hold,” Mr. Taler said.

One of City Arts’ summer interns, Alana Miller, is a 19-year-old student at Washington University in St. Louis. “The most common reaction I get from people who walk by is that they’ve seen these benches here their whole life and now they get a chance to restore them,” she said.

jakasie@nysun.com