The gaping hole in Atlanta's patchwork downtown could be filled with verdant green space and new roads that surround a sprawling passenger terminal to serve a busy network of buses, rail and streetcars.

Almost two decades after planners first offered up a proposal to overhaul the "Gulch," a group of developers will unveil three "conceptual drawings" today that show possible designs to turn the sunken tangle of parking spaces, vacant lots and rail lines into a key transit center. Far from set in stone, they are a starting point for the months of planning that's to come.

It's an important step in the lengthy effort to develop a "multimodal passenger terminal" that would anchor the area. Cleveland-based Forest City Enterprises Inc. and Atlanta firms Cousins Properties Inc. and The Integral Group LLC hope the project can pull together buses, trains, light rail and streetcars into a central stop.

"This is just the beginning of something great to come," said Jim Richardson, a senior vice president at Forest City.

The Atlanta Journal-Constitution got an early glimpse at the drawings before their release at tonight's meeting.

One shows a sprawling terminal with a route going through the center of a building for the city's new streetcar line, and each includes levels for bus stops, trains and other transit. New roads and parks are envisioned around the development, along with links to Five Points and Philips Arena. Several floors of office space above the building could be marketed to businesses in the transportation sector.

At least 20 other studies have been launched over the years to overhaul the site. Project plans for the area were unveiled in 1994 during the pre-Olympics building boom, but funding never followed. Other efforts to redo the area also languished in the 2000s, when proponents saw it as a possible center for commuter rail lines.

This time, though, the contractors have a $12.2 million contract from state transportation officials for the master plan, seed money they hope will spur more public and private investment.

The proposals now call for a terminal to bring together

MARTA, rail lines, bus routes and other forms of transportation in the prime location between the Five Points station, the CNN Center and the Castleberry Hill neighborhood.

One study released this year projects it could bring more than 15,000 new jobs to the area over 30 years, though some analysts expect the impact to be milder.

Over the next few months, the public will get a chance to weigh in on the different designs, starting with tonight's meeting. The preferred plan, which could be a mixture of the three designs or something entirely different, could be picked by October. Construction could begin as soon as late 2013.

"I see this as a game-changer in Atlanta," Richardson said. "It's the largest infrastructure project since the airport, and it will be as significant an impact as Hartsfield."

Meeting tonight

The ideas will be discussed at a 6 p.m. meeting Wednesday at the Atlanta Department of Watershed at 72 Marietta St.