“Once you tear it down, it’s gone.” Les Klein repeated one of his most striking statements from his presentation at IdeaCity not once but twice when I spoke to the architect a few days later. It succinctly sums up Klein’s opinion of the Gardiner, an expressway that has been on the city’s chopping block for about 20 years.

It would be hard to live in Toronto and not be familiar with the Gardiner Expressway. Officially named the Frederick G. Gardiner Expressway, it’s not only a visible icon running across the city (all the way from the junction of Highway 427 and the Queen Elizabeth Way to the Don Valley Parkway), its to-tear-down-or-not-to-tear-down status has been making headlines since 1990.

Currently, Waterfront Toronto sees the thoroughfare’s demolition as a key element of their Waterfront Revitalization. The $10 million environmental assessment consultation process began in March, but so far the only action the city has seen is the demolition of the section from the Don River to Leslie Street.

But that, according to Klein, is more than enough. When the city announced plans flatten a second phase of the Gardiner, he began thinking about possible alternatives. Then three years ago, he was taking part in Ride for Heart, a 75-kilometre charity bicycle tour where riders take over the Don Valley Parkway and the Gardiner Expressway. “It came to me,” he says. “Why can’t we ride for heart 365 days a year?”

Much like New York’s recently-opened High Line, the Gardiner, says Klein, calls for not demolition but adaptive reuse – a specialty of his firm Quadrangle Architects . His Green Ribbon proposal calls for a green roof to extend along the elevated section of the expressway, creating seven kilometers of pedestrian- and cyclist-friendly pathways.

Accessed via stairs and ramps at all intersections, the Green Ribbon would also have elevators and concessions at the busier junctions. From melting snow to lighting, the whole project would be self-powered by wind turbines and photovoltaic systems lining the whole seven kilometers.

Klein says that Green Ribbon would also improve safety on the Gardiner itself by blocking snow and rain – not to mention sun glare – from impairing drivers and slowing traffic. “It’s the art of the possible,” he says. “Every time I thought about a problem, I found a solution.” While Klein is quick to add that if ever actually built, the project would likely change or adapt considerably from its current stage, “the concept has strength,” he says.

The total cost to build Klein’s Green Ribbon would be upwards of $600 million. However, he adds, the next phase of demolishing the Gardiner would costs $300 million, and the total estimated cost of flattening the expressway would be around $1.5 billion.

The demolishing doesn’t just take a financial toll, says Klein. “The most green thing you can do is not sending something to a landfill,” he says, adding that the amount of energy required to dispose of all the rubble would be staggering.

Meanwhile, the Green Ribbon could decrease the heat island effect in Toronto, while adding green space and giving the people living around it a completely different kind of view. But most importantly, he says, a concept like this stops the city from making a decision that it’s not ready to make yet. “Once we take down the Gardiner, it’s gone for good,” he reiterates one last time.

The point of Klein’s idea is to shift the discussion away from the tear-it-down-rebuild paradigm. “It’s time to think about the Gardiner in a different way,” he says. The Green Ribbon is intended to get Torontonians reflecting on what the Gardiner once was – and what it could be in the future. “Cities are often judged by how they treat their heritage,” he says. “40 years ago, the Gardiner was a symbol of progress, a symbol of success, a symbol of power. You can’t just snap your fingers and say ‘that doesn’t matter.’”

What do you think? Those who know Toronto: is the Gardiner a city icon or an eyesore? Is it an essential traffic artery or a hindrance to the Waterfront Revitalization? Non-Torontonians: what major planning problems does your city face, and how has the city tackled those problems?