Achild dancing in a field of pointillist flowers. A dark-eyed likeness of Edgar Allan Poe. A waaay-larger-than-life still life of inky eggplants, crimson peppers and a head of lettuce. In Philadelphia, the painting, if not the writing, is on the wall -- this city loves outdoor art.

In styles ranging from impressionism to pop, more than 2,500 outdoor murals grace the exteriors of Philly rowhouses, skyscrapers, parking garages and public schools. Officials claim Philadelphia has the most such artworks of any city in the world.

Intrigued by these alfresco frescoes, my husband and I recently hopped on one of the twice-a-week trolley tours given by the Philadelphia Mural Arts Program. MAP, which began in 1984 as part of a government anti-graffiti campaign, now is responsible for installing murals in more than 100 communities a year, working with artists, neighborhood activists and landlords whose blank walls just might "capture a neighborhood's identity through art," said program director and founder Jane Golden. "These murals are like the autobiography of the city." Opera singer and South Philly native Mario Lanza, for example, looms from the side of a funeral home on South Broad Street. Poe's dour portrait peers out over his former Spring Garden 'hood.

Because so many murals pepper the landscape, trolley tours take in just one neighborhood at a time. Some roll past grand-scale works in Center City or colorful murals in Latino North Philadelphia. For our trek, we boarded a trolley at Rittenhouse Square and headed across the Schuylkill River into West Philadelphia. (October is a particularly easy time to go wall-to-wall on the wall art; it is Mural Arts Month in Philadelphia, which means special tours with food, talks and sometimes music.)

On our trip, the guide was local artist Kevin Gardner. As we zoomed into West Philly, Gardner expounded on the evolution of the mural program. "We used to paint with a thousand shades of beige, because all the materials were donated," he said.

After the program became part of the Philadelphia Department of Recreation in 1996, aggressive fundraising and private donations spurred grander, more colorful murals. Today there's a waiting list of neighborhoods and organizations that want to sponsor murals, and artists jockey for the honor of climbing scaffolds and applying their designs to blank walls. Local artists paint most murals, but some works are by schoolkids and a few even credit big names, such as the late Keith Haring, whose trademark jubilant figures cover a facade at 22nd and Ellsworth streets.

The Spring Garden Street Bridge features an open-air portrait gallery with cheerful faces (a little girl in pigtails, a dreadlocked dude) and abstract, quiltlike squares in purple and lavender. Gardner, a convivial guy who had assisted on several murals, pointed out dozens of other works. A two-story Patti LaBelle in a paisley poncho grooved on the side of a rowhouse. A farmscape with grazing horses and a red barn loomed above the real-world crops of a community garden. A ghostly image of a now-razed church shimmered from a red brick facade near its former site. Flesh-and-blood residents sitting on porches or working in flower beds waved to us, and a few tourists tried to hitch a ride.

Like some areas dolled up by MAP art, West Philly isn't postcard-pretty. Boarded-up town houses with sagging porches alternate with well-kept properties and gardens. But even on the grimmer blocks, murals brighten the scene: an African American grandmother working on a quilt, a triptych of fish and bridges done in muted pastels.

"Murals are the opposite of broken windows," said Golden. "They end up being hopeful, and they help to rejuvenate neighborhoods."

We wheeled past images of schoolchildren with their books or reaching for stars, and a dapper full-length portrait of singer-actor-activist Paul Robeson, who retired to Philly. Other murals simply startled with their beauty, such as Parris Stancell's "Peaceable Kingdom" at 4800 Parrish St., a stylized scene with ancient-Egypt-looking figures on a background of swirling blue vines and bubbling waves.

Murals also deck the walls in downtown Philly's traditional tourist zones like Rittenhouse Square and Center City. So later, a MAP brochure in hand, we followed a three-mile-plus loop past works including "Philadelphia Muses," a surreal tableau of dancers, musicians and dreamers, and "Famous Franks," a pop-arty collage of "franks" from FDR and Benjamin Franklin to a hot dog -- ha! After a few blocks, blank walls started to seem more unusual than murals.

As Gardner had said, "Murals have changed the face of Philly. The city really has the feeling of an outdoor gallery."

October is Mural Arts Months in Philadelphia, where more than 2,500 such works grace the city's rowhouses, skyscrapers and schools. Above, "Philadelphia Muses" is at 13th and Locust streets. Right, Paul Robeson adorns a wall on Chestnut. This rural mural in Philadelphia features a real-life corn crop growing in a community garden.