Kudzu smothers the old steel tracks. Broken bottles, chairs and grills litter the gray wooden crossties. But the derelict railroad that circles the city may have a bright future bustling with joggers, cyclists and commuters.

Atlanta's civic leaders envision the bleak railroad alleyway as a lush "emerald necklace" of trails, parks and public transit, a necklace that could transform a poster child of urban sprawl into the archetypal city of the 21st century.

The massive redevelopment plan -- known as the "Beltline" -- would convert the 22-mile loop into a paved trail and streetcar line linking 45 historic neighborhoods and creating more than 1,200 acres of parkland. The proposal has captured the imagination of many in the city and sparked a rash of real-estate deals.

But formidable political and financial hurdles must be cleared for the project to move forward.

Among them: a vote by the Atlanta City Council on Monday on whether to establish a tax district designed to raise $1.7 billion to fund the Beltline. If approved, property taxes collected on new developments in the district would pay for the parks, transit system and trails. Cost of the project is estimated at $2 billion to $3 billion.

The Beltline has a good chance of becoming reality -- eight of Atlanta's 15 council members are sponsoring the legislation.

"The Beltline would make Atlanta a new kind of city," said Alexander Garvin, professor of planning and management at Yale University and president of Alex Garvin & Associates, a New York design team. "The transformation would be staggering."

Garvin analyzed the Beltline's green space potential for the Trust for Public Land last year, and is astonished by the vision of Atlanta's officials. "No other city has this momentum," he said.

After the Civil War, the city built a railroad around its industrial outskirts, enabling freight trains to transport the South's cotton to the world.

Atlanta is now framed by highways, which lead to suburb after suburb. Of the 4.7 million people who live in metropolitan Atlanta, fewer than 500,000 live in the city.

With Atlanta's metropolitan population predicted to increase an additional 2.3 million by 2030, the city's mayor, Shirley Franklin, has identified the Beltline as a way to steer economic development toward the urban core. An unlikely coalition of city officials, private investors, community leaders and environmental groups has rallied behind the concept.

The Beltline idea was first proposed by an architecture student at Georgia Institute of Technology. Ryan Gravel, who developed the concept for his master's thesis in 1999, now works for the Beltline Partnership -- a steering committee set up by the mayor -- honing the design of the loop and building public support.

But the Beltline faces many unresolved questions. In September, a panel of transportation experts issued a report saying that large portions of the loop -- particularly the low-density, low-income neighborhoods in the west -- do not have sufficient ridership to support trains or trolleys. Nevertheless, some conservation groups are racing to secure land ahead of developers.

"This is one of our top national priorities," said James Langford, Georgia's director of the Trust for Public Land, a national land conservation group that recently paid $4.4 million to secure 41/4 acres around the Beltline. "We have to jump in and purchase this land before it's too late."

The race between environmentalists and developers highlights the different -- often competing -- visions of the Beltline. Some enthuse about the green trails and public transport, while others focus on adjacent development. "This is the most important planning event Atlanta has ever had," said Liz Coyle, a resident of the Virginia-Highland neighborhood who set up the Beltline Neighbors Coalition, which hopes to curtail mega-development. "If we do not get it right, it will be chaos."

Last year, a suburban real estate developer, Wayne Mason, bought 70 acres of the northeast portion of the Beltline corridor. He pledged to donate half the land to the city, but residents are concerned about what will happen with the remaining 35 acres.

In Bankhead -- where 83 percent of the residents are black and the median household income is $25,537 -- many stores are vacant, their parking lots sprouting weeds and scattered with glass. Many residents here did not seem to know about the Beltline's proposal to convert 400 acres around nearby Bellwood Quarry into a park and lake.

Robert D. Bullard, a sociology professor and director of the Environmental Justice Resource Center at Clark Atlanta University, is skeptical of the Beltline's claim to link neighborhoods and foster diversity. He said the proposal represents a tourist-orientated marketing campaign that makes no attempt to transport poor black people without cars to work.

Gravel acknowledges that the Beltline could end up creating a circle of privilege in the urban area, raising house prices and pushing poor people out to the suburbs, but he said that gentrification is happening.

At least, he said, the Beltline Partnership's redevelopment plan will attempt to distribute growth equally, setting up 12 development nodes in the rich and poor areas of the Beltline.

"This is just the beginning," Gravel said. "Atlanta is adolescent, but we're growing up, and we're learning how to build our city in a smart way."

An artist's rendering shows proposed light-rail lines, parkland and a mixed-use development on the Beltline Project.