If you want to experience the work of street artist Gaia in its full scruffy glory, see it in the wild.

Drive south down North Collington Avenue, past Biddle and Eager and Chase. You will despair of spotting anything fresh in one blighted block after another. But slow down as you near Ashland. On the corner of a string of boarded-up row homes is an image you register with pleasure and relief: a portrait of a carrier pigeon as a natural creature with an almost unnatural poise. It's a jolting and precise piece of poster art. Mysterious and witty, it carries a kinetic charge. This pigeon appears ready to take wing. What's holding him back? Could it be the patch of wing that someone has torn off the wall?

Gaia succeeds at pulling his viewers into neglected areas. Actually, he lives in one, sharing half the top floor of a dilapidated warehouse off Greenmount with seven or eight people (the number varies according to how many brothers or friends crash there for a season). There's a metaphor behind his use of a carrier pigeon as a recurring image. Standing on his fire-escape staircase, he's eager to explain it.

He says he uses the carrier pigeon only partly to introduce a live creature into moribund neighborhoods. "It's a carrier pigeon: it's trained by man," he explains. Gaia wants to prod his viewers into realizing that people create urban environments — sometimes for better but mostly, these days, for worse .

He takes the name of Gaia, the Greek earth goddess, to protect himself from being charged with vandalism. What he does is technically illegal, but authorities have never threatened him in Baltimore. In other cities, he says, "I have talked to a lot of policemen, but I have managed to assuage them." His disarming manner may have something to do with that. He wears a mask in photographs to preserve his anonymity. But when you see him with his mask off, sporting a cap and a beat-up jersey, he's as open, scampish, approachable and humorous as the savviest, most hopeful member of "The Bad News Bears."

He speaks with a combination of youthful slang and intellectual fervor; after all, he graduated from Maryland Institute College of Arts just last week. He uses "chill" as an adjective and "crushed" as a verb meaning "conquered." He notes that Americans resist the homogenization of culture and architecture in European social democracies because "we just don't jam that way. We celebrate what's 'authentic' and 'individual' to a fault — to a fault, because we end up marketing it."

Although his reputation has spread around the city, the country, and the world, he's an artist in his youth. Engaging and exuberant — not pretentious or self-conscious — he knows what he's doing, and he loves it.

"I'm really targeting the notion that you can plan a city," Gaia says. "Earlier in our history, a lot of cities had a much slower, more organic development, and it made for a robust mixed usage, and for a street scene that was much more lively."

Making prints from linoleum blocks, blowing them up to various poster sizes and putting them on buildings with wheat paste, Gaia seems to act like a mad scientist firing cells, catalyzing new life in urban corridors without pretending to know exactly where it's going. But he's crazy like a fox — my vote for Gaia's next seductive animal figure.

Passersby could rip his work down in whole or part, and other street artists could replace it. The city could tear the buildings down in a week, a month, or a day. What matters to him is prodding conversations on actual city streets that continue on the virtual streets of the Internet, where Gaia's artistic cousins on every continent track each other's work.

If a viewer doesn't immediately get the nuance of that carrier pigeon, that's "chill" with this ebullient young artist. What's important is igniting a response.

One of his eeriest poster images, a mystical bear with all-seeing eyes, has all but disappeared from Greenmount Avenue. Down the street, a wall-full of graffiti tags has lasted for a decade. Gaia savors the irony: "You'd think the thing that looks more spontaneous would disappear."

But graffiti was always about marking a public space and appropriating it. Street art is about sharing it and debating its proper use. He smiles at the statement that the bear's eyes survive — once you spot them they follow you down the street and pierce through the back of your head as you pass, like the eyes on the poster in "The Great Gatsby." Gaia also notes, with delight, that a mile north on Greenmount, a rooster-man on the side of the entryway to a walled-up store survives in "very pristine" form.

Gaia says that his way of getting to know a metropolis — whether Chicago and St. Louis or Seoul and Madrid — is to "bike around and survey it — and if I'm a guest in the city I'll ask for the most 'ghetto' neighborhoods." He also does a lot of online research to make sure a building is abandoned before he puts a mark on it. For his ongoing "Legacy" project, he's dug into the history of each site, using resources like The Baltimore Sun to analyze which decisions determined the fate of neighborhoods and who was responsible for making them.

He first got to Baltimore four years ago. He actually grew up on New York City's Upper East Side — as he jokes, "cream of the crop, baby!" His father is a "well-off financial adviser," his mother a holistic health counselor. "I was always an artist," he says, "and I had illusions of doing graffiti for a little bit." Street art came to him serendipitously. A MySpace contact introduced him to it. Once Gaia discovered the work of the female street artist known as Swoon, he swooned.

Swoon also works wonders with posters, has an open and self-aware attitude and a complex relationship to how she plies her trade. Swoon has said, "When I paste something to the wall, I'm sort of hoping that that object will ultimately be destroyed. I want it to be outside and part of the city landscape and to rot away, so that it's never going to stick around and be a permanent thing." But Swoon displays her work in galleries, too.

Gaia also prizes the "happening" part of putting art up where citizens least expect it. But like Swoon he aims to go after audiences every which way.

Right now, Baltimoreans can experience his art in a lucid, concentrated context and with almost as much immediacy as it has in the streets. Simply walk down W. Baltimore Street between Howard and Eutaw Streets. When you hit the number 307, you'll see wood-and-glass doors that would better fit a stylish saloon in a nightlife district than a building in a nondescript block whose big-name tenant is a 7-11.

For the next three days this building isn't empty. From the sidewalk you can see, perched on the walls, strange creatures like an enormous double raven with wings so dense they seem sashed and an attack rabbit poised to strike like a lion on the pounce — courtesy of Gaia.