Colorful faces by the artist Phetus are among blocks of sprawling murals in Brooklyn’s Bushwick neighborhood. (James F. Lee/James F. Lee)

“Bushwick is the hippest place in the whole entire world,” said our guide, Izzy.

She pointed to a doorway across Bogart Street crowned by two sets of bubblelike white teeth and pink gums. It’s the work of graffiti artist Sweet Toof. To the left of the doorway was a life-size poster of a woman in a black cloak. The brick wall is alive with stickers, stencils, spray-painted illustrations and graffiti tags.

Izzy and her fellow guide, Mar, were leading our international group of 23 through the gritty yet vibrant streets of Brooklyn’s Bushwick section, the choicest canvas for graffiti and street art in New York. Ours was one of several New York tours offered by Free Tours by Foot, which specializes in offbeat tours in cities nationwide.

Not long ago, Mar told us, Bushwick was a neglected, desolate remnant of a once-thriving Brooklyn neighborhood. But street artists had long gravitated here, drawn by the ample industrial wall space, a natural canvas for the outdoor artists’ work. Then, as nearby Williamsburg gentrified, other aspiring artists started moving into Bushwick, where they could acquire cheap lofts in the abandoned factories and warehouses that still dominate the neighborhood.

If you go: Bushwick

Our tour started at Brooklyn’s Natural grocery on Bogart. The grocery wall is painted with a lively scene of a boy tending a garden of talking mushrooms, peas and carrots. Random cherries, strawberries, grapes, lemons and limes also adorn the wall. And are those tiny flying pigs?

Graffiti, of course, is illegal unless you have permission to use a surface. As we navigated the streets, we learned what’s legal and what isn’t. We followed Izzy and Mar to Boerum Street, lined on one side by brick warehouse walls and with the metal fence of United Transit Mix Co. across the street. This is as bleakly urban as it gets. On the warehouse side, stretching the entire length of the street, is one complicated piece after another, a riot of colors and shapes, figures and words. In each piece there’s a message.

Across the street, the fence is lined with writers’ tags, or signatures, and with throw-ups, simple quick drawings that also identify the artists. Earlier, Izzy had pointed out a tag that read “Cartoon Bacon.”

“A tag can be a way for an artist to get his name out,” she said. “He’s spreading his name everywhere. People ask, ‘Who’s Cartoon Bacon?’ ” When Cartoon Bacon does a piece somewhere, it will be highly noticed.

Back on Boerum Street, Mar stood in front of a piece by an artist called Cod. He explained that Cod and his crew would work out the details of the design beforehand and then execute the piece at night in a matter of hours. Cod’s tag prominently caps the work, which also includes the tags of his crew. This piece is in the “wild style” of interlocking letters and arrows. Other styles include bubble style, with large, rounded letters; stencils that can be done in the artist’s studio and then spray-painted quickly against a wall; and stickers, which the artist can mass-produce and then slap onto a surface.

Across the street, an artist’s tag is clearly visible near the top of a nearby factory tower. A tag in a hard-to-reach spot is said to be in heaven, said Mar, noting that the artist taking risks can gain respect from fellow artists. If the work stays in its heavenly spot for at least five years, it becomes a landmark.

At first, looking at these streets can be a bit frightening, especially given graffiti’s connections to gang activity. But where gangs mark territory, artists present a more positive message. “Graffiti artists are like scribes leaving a message for their community,” Mar said. It can be a celebration of life or something as simple as the tag “Cornbread Loves Cynthia.”

We left the neighborhood near the grocery for the long walk to the Bushwick Collective. This was the brainchild of Bushwick native Joseph Ficalora, who wanted to channel the positive energy that goes into graffiti and lessen the need for illegal expression. He got building owners to offer wall space and then invited street artists from across the world to use Bushwick as a canvas.

We watched as street artists painted blank walls in broad daylight without fear of arrest. In just a couple of years, those artists have transformed the urban landscape around Jefferson and Troutman streets and St. Nicholas Avenue into an ever-shifting kaleidoscope of color. People come here to see new works by their favorite artists, or just to see something new.

Josefina Samuelsson, from Sweden, was excited to see new images. “A lot of new artists’ names,” she said. “It’s fantastic to see.”

This is a theme: Bushwick’s walls are a constantly changing canvas. In the days between taking the tour and writing this story, I learned that my favorite piece, “The Whale” by Nychos, painted on the side of Tutu’s restaurant, on the corner of Bogart and Varet streets, had been replaced by a different artist’s work. Gone was the intricate detail showing a killer whale from the side, cut out so that the skeleton and internal organs were visible, an astonishing piece done under cover of darkness. The whale had been up about a year.

But that’s the life cycle of street art.

Today, block by block, life is coming back to Bushwick, driven by the art on the walls. It brings people to the neighborhood who may then stay a while and eat lunch or have a coffee. Stores serving the artistic community pop up, and the whole community starts to rebuild.

Meanwhile, visitors learn, as Izzy said, that graffiti isn’t “just a tag on the wall. It means something different than vandalism.”

After all, she said, “If it makes you smile, it can’t be bad.”

And at least I got a picture of “The Whale” before it vanished.

Lee teaches journalism at Bucknell University.