John P. DiGiovanni, vice president of Trinity Property Management, which operates The Garage on JFK St. and the Atrium on Church St., agrees that the future looks good for Harvard Square's economy.

"I do sense that it's picking up," DiGiovanni says, pointing to the end of last year and early this year as a low point for Square businesses. Especially with the new school year beginning, he says, there's a "good feeling" among businesses right now.

Richard Getz, who manages property rented by Urban Outfitters, The Lodge and The Greenhouse Restaurant, says that the businesses he works with have been doing well, due in large part to the Square's stable economy.

And it is that stability that makes the Square attractive to prospective retailers and office-renters. Once space is rented in Harvard Square, especially retail space, it is usually rented for a long time.

The construction era is nearly over in the Square, local developers say, simply because there is very little space left.

With partner John Hall, Friedman is planning to demolish the Harvard Manor House Hotel and replace it with a six-story building that will open up 100,000 square feet of new retail and office space. The demand for that space, Friedman says, is still high.

"There is tremendous demand in Harvard Square," Friedman says.

He and DiGiovanni say that prime retail space is renting at about $100 a square foot and the best office space at $25 a square foot, prices comparable to those of top locations in Boston.

The nearly-complete 113-room Inn at Harvard, on Massachusetts Ave. at Harvard St., will be booking its first guests for late October, and Robert Banker reportedly has plans to develop some of the last available space in the Square, an empty lot on Eliot St.

After that, there will be little room left.

"I think we're seeing the end of a 10 to 15 year cycle of construction," Friedman says. "There are no more available sites."

DiGiovanni says that he currently has no vacancies in his rental space, and that there is little turnover, especially in retail.

"It's sort of a private club," DiGiovanni says. "It's difficult to get into."

Some businesses have left the area, including Underground Camera, Bennetton, Ching Hua restaurant and Sam Goody's, but for the most part, retailers are eager to get into the Harvard Square market. Those already here remain upbeat about the area's future.

"We're lucky to be in Harvard Square," Friedman says.