A Boston businessman's proposal to build a 1,000-foot, 75-story glass-and-steel building that would tower over all others is a bold move in a city that favors colonial era church steeples over skyscrapers.

Steve Belkin's proposed tower would top the city's current tallest building by more than 200 feet and 15 stories, reflecting a resurgence in the downtown commercial real estate market, observers say.

"I think it's going to make a lot of our other buildings look very boring, quite honestly," said Frank Nelson, a Boston-based executive director with the commercial real estate services firm Cushman & Wakefield. "We need it."

The design by renowned Italian architect Renzo Piano emerged last week in response to Mayor Thomas Menino's call in February for private development proposals to replace an aging city-owned parking garage in the heart of the Financial District.

Officials in Boston and other U.S. cities typically seek to rein in developers' wishes to build high above neighboring office buildings, but the sky was the limit for Menino. He encouraged a bold architectural statement to surpass the John Hancock Tower, which for three decades has stood as New England's tallest building at 60 stories and 792 feet.

The Hancock anchors Boston's Back Bay section along with the 42-year-old, 52-story Prudential Tower.

In the nearby Financial District — home to the likes of Fidelity Investments and State Street Corp. — most tall buildings top out at around 40 stories. The last time a new Boston building of more 40 stories went up was in 1987, with the completion of the 46-story One International Place.

In a city that has managed to save historic structures such as King's Chapel and the Old Statehouse from overshadowing high-rises, reluctance to build high runs deep. A state law restricts new buildings that would cast a shadow on Boston Common, and past proposals to build 50 stories or higher in the Financial District have failed to secure city approvals.

"We are an old city that is not that tall, so we take a look at each project and make sure it is appropriate," said Susan Elsbree, a spokeswoman for the Boston Redevelopment Authority, the city agency that will review Belkin's proposal.

So when Menino called for a project taller than any the city had seen before, the mayor and others hoped several developers would respond by last Monday's design-submission deadline, leading to a competitive selection process.

But in the end, there was just the proposal from Belkin, the founder of credit card and travel companies, and part owner of two Atlanta pro sports teams, the Hawks and Thrashers.

However, real estate officials say Menino's failure to bring in more than one development proposal is not an indication that the downtown commercial real estate market has failed to break out of a five-year slump.

They say the office building market is starting to catch up with recent booming residential growth in high-rise downtown condominiums. They cite the Boston office market's vacancy rate of 8.2 percent in this year's third quarter — the lowest in more than four years, according to the commercial real estate firm CB Richard Ellis.

Observers say Belkin was the only developer to come forward because he has an edge over rivals to make the most of the hemmed-in Winthrop Square development site, where the skyscraper would replace the parking garage on Federal Street.

Because Belkin already owns a mid-rise building adjoining the oddly shaped site, he could expand his skyscraper to the space occupied by his existing building, which could be torn down.

"He really had the edge coming in," said David Begelfer, chief executive of the Massachusetts chapter of the National Association of Industrial and Office Properties. "The space issue has made it a much more limited opportunity for other developers."

Belkin wants to call his skyscraper Trans National Place, after his company, Trans National Group.

Piano is a Pritzker Prize-winning architect known for his work on such projects as the Centre Pompidou in Paris and The New York Times Co.'s new headquarters in Times Square.

His Boston design would create 1.3 million square feet of office space, with a mix of retail and restaurant space on lower floors. A 1-acre park would be built at ground level, with more public space on the building's roof.

There is no specific timeline for the project, and the city says its review process could involve more than one stage before the final building design is approved. But real estate industry officials say they're optimistic the project will be built, given the recent rebound in the downtown office space market.

Don't expect Boston to resemble Manhattan's skyline. The site for Belkin's tower is one of the last prime pieces of real estate available for development in the downtown core, and new projects on the city's South Boston waterfront are height-restricted to provide unobstructed flight paths to nearby Logan International Airport.

"I think the site for this new building is so prime that it's the last of the great downtown building sites in Boston," said Nelson, of Cushman Wakefield.