It's not often that such skateboarding tricks as ollies, grinds and backside tail-slides are on display in a fine arts gallery, but "Session the Bowl" at Deitch Projects in SoHo is an unusual art show.

The exhibition, running through Saturday, includes more than 30 skateboarding-inspired works, including paintings, photographs, collages and one pornographic skateboard. Its main attraction, though, is "Free Basin," an enormous, elevated, kidney-shaped wooden bowl. Depending on their interests, gallery visitors might view "Free Basin" as an innovative sculpture or an architectural exercise. Still others will regard "Free Basin" as a gnarly thing to ride a skateboard on, and this explains why dozens of local skateboarders drop by to "session the bowl" (get together and skate the bowl) during gallery hours.

"Free Basin" is a skateboarder's dream. "It's a good thing in winter, having somewhere indoors to skate. It rattles your bones a little when you fall in the cold," says Jack Fitzgerald, a 27-year-old writer who has been a regular at Deitch since the show opened last month. "Free Basin" has another advantage over the cold city streets. "This is a bowl, which means it's easier to feel the velocity in the movement," he says.

"It really is a live sculpture," says gallery owner Jeffrey Deitch. "It's not a form that you just look at. It is completely experiential."

"For me, looking at it, it is almost like a live Jackson Pollock painting," Deitch adds. "It has aspects of a live painting, where the movements of the skaters remind me of the gestures of an artist making a drawing or a painting."

The skateboarders, mostly guys in their twenties and thirties, wear jeans, sneakers and various combinations of long- and short-sleeve T-shirts. Their jeans are really baggy, which means that this show could also be appreciated as an exhibition of boxer shorts. One by one, they skate for a minute or two while the others stand on the high platform surrounding the bowl, poised to jump on their boards and ride the seven-foot drop to the bottom. Their boards make a deafening rumble, so conversations among skaters and spectators must be bellowed.

Besides keeping their balance, one of the toughest challenges for skateboarders can be finding places to skate. During the California drought of the mid-'70s, skateboarding's best and bravest raided backyard swimming pools, where, defying trespassing laws as well as laws of physics, they skated up and along the sloped sides of emptied pools, inventing a variety of tricks that involve grinding the axles of their boards against the coping -- the tiles along the pools' edges.

"Free Basin" was inspired by those empty pools, and its edges have coping, too. The bowl itself is 40 feet long and 25 feet wide at its widest point. Constructed of plywood, it weighs five tons, according to Simparch, the artist collective that created the sculpture in 2000 for an exhibition at Chicago's Hyde Park Art Center.

"It was a conceptual endeavor," says Steve Badgett, who runs Simparch along with Matt Lynch. "It relates to a history in sculpture that has to do with very large formalist or minimalist pieces."

While creating the piece, he says, he remembered stories he had heard that skaters -- always on the lookout for new spots to skateboard -- had ridden on sculptures by Richard Deakin and Richard Serra. "We were building this very difficult form, and we happened to be tailoring it to this particular subculture," says Badgett.

After its debut in Chicago, "Free Basin" traveled to the Wexner Center for the Arts in Columbus, Ohio, before it was shipped to Kassel, Germany, for last year's Documenta 11 exhibition.

"Free Basin" is for sale, though the Deitch skateboarders are not included in the asking price, which is around $80,000. Whoever buys the sculpture has to commit to maintenance, says Deitch, and there are other issues, too. "We've had some offers from skate parks, but we would like to maintain its meaning as a live sculpture," he says. "We'd like someone to have it who would put it in an art context."

Badgett is more ambivalent. "It would be an awkward piece for a museum collection," he says. "People in the art world say it should go to a museum. But then it would be like a violin that doesn't get used."

Some die-hard skateboarders find it odd that an art venue is exhibiting a skateboarding bowl. "I wouldn't say that this is art," says skateboarder Andrew Holmes, a 31-year-old bartender. "That's a bit pretentious. If you ask me, it's a bunch of guys getting their aggression out."

Another Deitch regular, Jocko Weyland, authored "The Answer Is Never: A Skateboarder's History of the World," which was published by Grove Press last fall. (The title is a skateboarder's reply to questions like: When are you going to grow up and stop doing this?) Weyland, 35, says the existence of this exhibition says something about how the once-underground skateboarding culture has changed. "There is this idea that skating is this urban activity and it's cutting-edge," says Weyland. "And in a way it isn't, as much as it used to be -- it being in a gallery is proof of that."

Others revel in the celebration of their sport. "If you want to be intricate, we are performance artists, and everyone that shows up here is part of the show," says Dan Pensyl, 25, slurping down a can of Budweiser between rides. The shaggy-haired Pensyl is an accomplished skater who has sponsorship deals with several skateboard companies. "It's great when there's parties and girls from SoHo going around." Whether "Free Basin" is art or not, many of the gallery's visitors are entranced by it and its skateboarders, and they spend hours on the platform, peering down into the bowl, taking it all in.

Leanne Ng, visiting from Seattle, contemplates the skaters for much of an afternoon. "This is amazing," she says. "It's an incredibly unique concept for something like this to be in a fine-art gallery."

Back home, Ng, 26, works in an art gallery. When she returns, she'll tell her boss about "Free Basin," but she doesn't expect him to bring it to their gallery.

"Oh, I don't think so," she says, shaking her head. "We have mostly glass art."

Ryan Crase, in helmet, waits his turn to skateboard in "Free Basin," an enormous wooden bowl that is the centerpiece of the exhibition "Session the Bowl."Surrounding the performance art at SoHo's Deitch Projects are more traditional skateboarding-inspired works, including this installation by Thomas Campbell.