NEW HAVEN — For nearly three hours Monday, idealistic planners spun visions of gardens and swimming pools atop the New Haven Coliseum and multiplex movie theaters or interior parks within it.

Then, quite unexpectedly, Mayor John DeStefano Jr. walked into the room and delivered a decisive reality check: Forget about it, folks. It’s coming down.

The event, billed as the first public forum ever held on the future of the now-closed Coliseum site, was part of the Edge, the New Haven Fringe Festival. This is a feisty companion piece to the International Festival of Arts & Ideas.

Approximately 40 participants came to ARTSPACE in the Chamberlain Building, a stone’s throw from the shuttered Coliseum, to propose new uses for the structure.

Only one of the presenters, Richard Munday of the architectural firm Herbert S. Newman & Partners, put forth a plan entailing tearing down the Coliseum. That firm was hired by the city to come up with such a concept.

Munday detailed the components DeStefano favors, including moving Gateway Community College to the vacant Macy’s and Malley’s sites, moving Long Wharf Theatre to the rear of the Knights of Columbus tower, and building a hotel and conference and convention center as well as apartments, stores and an urban park.

However, the audience was much more enthusiastic about a range of proposals from other architects and planners, because all of them would retain the Coliseum.

A group of area high schoolers working with the ACE (Architecture Construction Engineering) Mentoring Program visualized apartments on the parking garage atop the Coliseum and multiplex theaters in the arena.

Alan Organschi of the Gray Organschi architectural firm proposed an outdoor movie amphitheater, gyms, pools or athletic fields atop the Coliseum and eight movie theaters within it.

Bob Gregson, an events planner, talked about taking off the parking garage and replacing the arena with an interior park.

Henry Dynia, a rehabilitation specialist for Neighborhood Housing Services, said the 2,400-car parking garage should be saved because, "The need for (downtown) parking will grow daily."

Dynia, who wants a museum, banquet hall or fitness center built in the Coliseum, said the gigantic structure "really makes my heart pound."

Then in walked DeStefano to let the air out of the balloons.

"It never created any economic activity around it," he said. "It didn’t even sustain a bar on the corner."

DeStefano said that although many suburbanites came to Coliseum events, "Surrounding towns do not see it as their role to put their tax dollars into it."

DeStefano, who closed the Coliseum last September, said he can’t bring Gateway Community College downtown and revitalize those streets with a hotel, convention center and new parking facilities unless he receives state subsidies.

He has asked Gov. John G. Rowland for $10.2 million to tear down the Coliseum. The money is uncertain because of the tough economy.

"Everything flows from getting it down," DeStefano said.

When the forum’s organizer Colin Caplan pointed out the many uses suggested by the panelists, DeStefano replied, "Be realistic. There are not investors lining up."

Coliseum Authority board member Matthew Nemerson said the agency had long studied the feasibility of luring movie theater operators and other businesses in order to save the Coliseum, but no idea ever worked.

Asked whether he foresees a new arena being built in New Haven, DeStefano said this might happen if a law were created allowing voters in a referendum to agree to pay for construction through taxes.

Toward the end of the discussion, Coliseum supporter and hockey fan Kevin Tennyson held up a picture of the New Haven Arena being demolished.

"As a sports fan, I feel bad," he said of the Coliseum’s pending demolition. "We hope to have a new one in our lifetime."