Like a boat ride at a fantastical circus, "City of Lost Children" takes its audience through bright green water as they marvel at a cartoonish harbor town populated by freakish inhabitants. The audience passes through metal rooms with circular gauges and mad scientists, they point at the talking brain bubbling in a fish tank and dodge the leaping fleas carrying magical potions. It's an alternate world lost in a nocturnal, greenish haze, an industrial turn-of-the-century Paris with cobblestone streets and menacing Cyclops.

The creators of this fantasy are French filmmakers Jeunet and Caro, the avant garde stylists whose previous film "Delicatessen" (1991) stirred the international film scene with its offbeat humor and outlandish visuals. The filmmakers relay an impressive vision, a cross between the surreal exaggerations of Terry Gilliam and the detailed, indiosyncratic animations of the Brothers Quay.

"City of Lost Children" follows the misadventures of Miette, a spunky 9-year-old leader of a gang of orphans. The children evade the wrath of the Octopus, Siamese twin sisters who run an orphanage and send the orphans on criminal scavenger hunts. Miette befriends One, a circus strongman whose "little brother" has been taken captive by the Cyclops and given to an evil scientist named Krank who lives in an offshore dwelling that resembles a cross between an oil rig and a castle.

Krank is a demented old man who is aging prematurely because of a fatal flaw: He is unable to dream. In his own mad scientist way, he kidnaps children, straps them into glass booths and attaches wires to their heads, hoping to steal their dreams and enjoy them for himself. His assistants are eccentric clones (all played by the same actor) who stumble through the angular hallways and laboratories secretly dreaming of being the original individual who patterned the others.

The film is a wonderous visual odyssey, a collection of hideous caricatures moving through a circus town of stained bricks and flailing shadows. It could be the postwar Vienna of "The Third Man" with its poor mobs and lean faces, the children staring out of nooks and crannies with wide innocent eyes. It could also be a future envisioned by Jules Verne, with video circuitry and homemade machines decorating a steam-powered culture in crumbling depression. Whatever its influences, the film is a superbly convincing journey through playful imagination.

The movie's themes are that youth is maintained through our ability to dream and that external qualifiers like size an age do not accurately depict one's "youth." When Miette's friends accuse her of befriending an older person, she says sadly, "He's not old. And you're not young," causing her friends to reevaluate their pessimism and saunter away in shame.

While the film was made in France, it's special effects rival anything that has come out of Hollywood in recent years. Utilizing computer graphics, one actor separately plays up to six different roles in individual shots, a sentient gaseous cloud wafts through the dank streets in search of a character, and a flea leaps from buildings, lands on dogs, and jumps onto peoples heads, crawling through magnified forests of hair.

As it draws to a close, "City of Lost Children" eventually deposits the audience back into the real world with a silly grin on their faces. The movie doesn't thrive on emotional depth and its story is simply an excuse to serve up its visual fantasy, but the trip is well worth the ride. Exiting the theatre with circus music blooping away, it's impossible not to relish the joy of imagination, even if you have to share it.