Zany ambition is the norm when it comes to Northern Spark, the free all-night art fest starting at dusk Saturday in St. Paul’s Lowertown.

There will be a 15-foot-tall bicycle-powered bat, an “existential” travel agency, a three-story video of New Yorkers spinning hula hoops, a water-balloon-throwing catapult shaped like the Foshay Tower, a gigantic hammock linked to video surveillance cameras and the 2 a.m. incineration of an 1,800-square-foot wood-and-cardboard house. Fire trucks are on standby.

“Oh, and there will be a kazoo band tromping around,” said Steve Dietz, the Spark’s chief organizer and impresario.

Of course. What’s a party without a kazoo band?

For its third incarnation, the Spark will close a dozen capital-city blocks, take over 37 acres of the Union Depot’s grounds, and run down to the Mississippi River.

Inspired by similar festivals in New York, Montreal, Paris and other international hot spots, Northern Spark was staged in Minneapolis last year, and both cities in its 2011 debut. This year’s St. Paul exclusive was prompted by the unusual availability of Union Depot, a long-closed train station that is being refurbished as a transit hub for Amtrak, bus service and the new Central Corridor light-rail line.

St. Paul did not provide any money for the 2013 events even though the city has been aggressively courting art projects for urban renewal and cultural branding purposes. Last year it helped the Minnesota Museum of American Art open temporary galleries in a refurbished downtown building. Now about $1.5 million in public art projects are in the works at Union Depot, and $3.25 million in mostly federal funds will be spent on Central Corridor art projects.

St. Paul’s Cultural Star program, which is funded by sales taxes, already has committed $24,000 toward next year’s Northern Spark.

“Sometimes you have these moments where a whole bunch of stars align and things go your way,” said the city’s arts liaison, Joe Spencer, who credited the cultural fluorescence to an eight-year initiative by Mayor Chris Coleman. “We put a vision out there of using the arts to help revitalize the downtown and now that’s coming together.”

‘We want this to be fun’

Funding for the Spark’s $155,000 budget this year came from local foundations, state and federal grants, corporate and private contributions.

Artists got money to cover their construction costs, which generally ranged from $500 to $2,500. Most are donating their creative time and many will be digging into their own pockets to pay for cost overruns.

Tom and Jennifer Carruthers, a husband-wife team of architects who recently moved to northeast Minneapolis from Brooklyn, got a local steel-supply company to help fabricate two frames, each 10 feet tall and 17 feet wide, that will hold video screens and cameras. Strung between them is a giant hammock on which visitors can lounge while viewing projected images of activities outside the structure.

“This uses surveillance technology and turns it back on itself,” said Tom Carruthers.

Elsewhere on the Union Depot site, visitors can use the “Foshaybuchet” — a catapult patterned on an ancient siege engine called a trebuchet — to lob water balloons containing magnetized bundles of colorful LED lights toward a steel plate. If everything works as planned, the LEDs will stick to the plate and coalesce into “modern graffiti art,” said Dave Bryan of the Hack Factory, a collaborative workshop in south Minneapolis that is building the apparatus.

Hack Factory artists are also creating a “firefly” wall of LED lights programmed to react to human motion, and they plan to have a team of artists creating steel constructions based on drawings done by Spark visitors.

“We want this to be fun, to make and do things that go back to the community,” said Bryan.

Then there’s the house that will be ceremonially torched by Hollywood Pyrotechnics, a firm specializing in fireworks displays. It’s an exact, full-sized replica by St. Paul sculptor Chris Larson of a famous 1960s modernist home by architect Marcel Breuer that stands on a bluff overlooking St. Paul.

With its pure white, wood-and-cardboard walls, the house looks like an enormous, walk-in birthday cake. Setting it afire at 2 a.m. on a summer night is Larson’s surreal tribute to a 50-year-old structure that “I’m very much in love with, especially after building it,” he said.