The gaping hole in downtown Atlanta could eventually be filled with a signature transportation hub featuring a great hall dotted with restaurants and retail. And it would be surrounded by greenspace and a new grid of roads that relegate the sunken tangle of railroads and parking lots now known as the "Gulch" to a distant memory.

A group of developers showed off three potential designs Wednesday for the "multimodal passenger terminal" that would anchor a redevelopment of the nearly 120 acres in the heart of the city. Cleveland-based Forest City Enterprises Inc. and Atlanta firms Cousins Properties Inc. and The Integral Group LLC hope it can pull together buses, trains, light rail and streetcars into a central stop.

The idea is far from complete. Private and public funding needed for the overhaul has yet to materialize and planners still need more time to finish off the design. They emphasized that the plan is far from set in stone, but just a starting point for the months of planning that's to come.

Still, they sketched out preliminary details to an audience of more than 100 people. The hub could eventually feature five rail platforms, 80 bus bays, space for street cars and freight rail, and plenty of parking for those who'd rather drive. The building would be a short walk from MARTA's Five Points Station and other attractions and would have office space targeted at the transportation sector.

Engineers would build two new east-west connections and a new north-south connection that would run parallel to Spring Street to relieve some of the traffic. The roads would be laced with sidewalks and bike lanes to encourage a bustling street presence.

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. City officials are hopeful, too, that the idea could transform the prime location between the Five Points station, the CNN Center and the Castleberry Hill neighborhood.

The three designs, though just starting points, are ambitious. They feature massive atriums and areas that could accommodate soaring office towers down the road. One rendering includes a terminal that stretches several city blocks over the chasm that now divides Five Points from the CNN Center. Another envisions an open area running through the spine of the building designed for street cars.

Another lofty hope: It imagines a network of commuter rail lines that link to Atlanta's suburbs and beyond, with a central hub in Macon and spurs to Augusta, Chattanooga and elsewhere.

Over the next few months, the public will get a chance to weigh in on the different designs. 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.

The finished product, though, could end up baring little resemblance to Wednesday's designs.

'These are very preliminary images," said John Schuyler, a principal with the FXFOWLE design firm, who is representing Cooper Carry architects on the project. "What's essential here are the fundamental characteristics of the schemes."

Future for 'Gulch'

The master development team for a multimodal passenger terminal will hold its meeting at 6 p.m. Wednesday at the Atlanta Department of Watershed Management at 72 Marietta St. in downtown Atlanta.

Numbers:

Nearly 120 acres

A $12.2 million contract

One study commissioned by Central Atlanta Progress says it could bring more than 15,000 jobs over 30 years