Atlanta's newest showpiece, a $750 million airport that opened for business recently, is raising expectations of a new boom for the southern city of glass towers and stately mansions.

Few businesses are looking forward more eagerly to the expansion of Atlanta as a major transportation hub than the convention trade. The city is about the size of Cleveland, but through prolific building of merchandise marts, hotels and convention facilities, it has turned itself into the nation's No. 3 convention city.

It is outranked only by Chicago and New York despite the lack of similar cultural or entertanment attractions of national repute. Unlike those cities, Atlanta's skyline is dominated by convention-oriented hotels.

To some people, that's one of the city's problems. Atlanta sometimes seems to be built more for outsiders than for those who live there. Even the new airport terminal, which will handle 80,000 passengers a day, will get about 73 percent of its business from passengers who don't go into the city but merely connect at Atlanta with other flights.

Most natives seek their nightlife in the suburbs, and "without" conventions, downtown would be totally dead," says Donald Ratajczak, an economist at Georgia State University. Evie Wolfe, who heads a convention-servicing business, Atlanta Convention Planners, agrees.

"Local business downtown isn't very good," she says. "People who work there eat lunch downtown, but people just don't go downtown after dark."

But much of Atlanta's future building is convention-oriented. John Portman, the city's premier architect and developer -- and, some say, the town's real city planner -- has announced plans for a new 1,500-room hotel near his Peachtree Center hotel-office complex, an 800,000-square-foot addition to his merchandise mart and two office towers with a total of 1 million square feet of space.

The Hyatt Regency Hotel, a Portmanesque atrium-style landmark that helped thrust Atlanta into the convention business in the mid-1960s, plans to add 400 rooms. And the Georgia World Congress Center, a huge exhibit hall near downtown's southside, is preparing to expand.

All this will put almost 4,000 hotel rooms within a few steps of each other. Considering the easy access by air, the answers to why conventions head to Atlanta seem to be: because it's there and because you can get there. h

The American Dietic Association, for instance, will visit this month because "there are a number of hotels centrally located," says Norine Condon, the association's assistant executive director.

But for all the catering to outsiders, Atlanta's convention complexes create an aura of vibrance that may be working to the city's advantage in attracting jobs. The hotels, with their glass towers, shops and fancy restaurants, for example, probably helped persuade Georgia-Pacific Corp. to build its 1.4 million-square-foot headquarters in the heart of downtown when the company decided to relocate from Portland, Ore., says Georgia State's Ratajczak.

The rash of hotel building also is spurring office building by concerns with a stake in downtown despite a current oversupply of space. The office vacancy rate in June was 12 1/2 percent, the highest in the nation, according to a study by Coldwell Banker & Co., the Los Angeles real estate concern. Kansas City ranked next with a downtown vacancy rate of 8.3 percent.

Marathon U.S. Realties Inc., a unit of Toronto's Marathon Realty Co., plans to build a 500,000-square-foot office building in Atlanta that eventually may double in size. Georgia Power Co. and Southern Bell Telephone & Telegraph Co. also are building office towers on the ourskirts of downtown.

Along with the new office building, many people see the character of downtown changing as Atlanta's subway system moves toward completion. The first part of the subway was opened last year; the whole system won't by ready for several years.

Subways should make downtown employment more attractive and accessible, and should help demand for office space. Until now, says Richard Bryant, Coldwell Banker's Atlanta sales manager, suburban office parks have dominated the local market for prime office space. But, he says, "I sense a revitalization of the downtown market here."