Jake Desko and Richard Friedman were light on their feet as they peered into a crystal blue sky and stretched toward a beam dangling above them from a crane.

It was just out of their reach but in a second it swung back. They snatched it, steadied themselves, pulled in down, squatted and quickly connected it to two larger beams.

And then the ironworkers repeated the process, performing an amazingly nimble dance, balancing on a beam only 4 inches wide and 24 stories high. A crane operator, equally talented at his trade, floated beams to the men he couldn't even see but who had blind trust in him.

They were among 190 workers who yesterday were on the construction site at Fifth Avenue and Market Street, using their skills to build Three PNC Plaza, Downtown's first new high-rise office building in two decades.

Tomorrow, Mr. Desko and Mr. Friedman and a crane operator will have the honor of "topping off" the structure, signifying the completed erection of 4,500 tons of structural steel for the $200 million skyscraper. As is the tradition of ironworkers, the final beam will be hoisted with an American flag and a Christmas tree on it. The beam, which will be signed by about 200 construction workers beforehand, will be set in place about 11 a.m. on the building's northeast corner.

"That's a real big deal," P.J. Dick Inc.'s Ray Monaco, the project's general superintendent, said of the topping-off ceremony, the completion of about 333,000 hours of work on the project thus far.

Construction of the 26-story structure -- 23 floors, two mezzanines, and one elevator penthouse -- is on schedule for mixed-use occupancy next year. Housed inside the building on Fifth Avenue will be offices for PNC and the international law firm Reed Smith; a 165-room hotel to be run by Toronto-based Fairmont Hotels and Resorts; 28 luxury condominiums starting at $500,000 apiece; retail shops; and an underground garage.

"We're really happy," said Gary Jay Saulson, director of corporate real estate for PNC Financial Services Group. "We think it's really going to be a positive contribution to the skyline of Pittsburgh.

"It's a fairly complicated project with its mixed use, the first one here, but that really makes it more interesting and one way it positively contributes to Pittsburgh."

Retail space will be on the first floor--tenants haven't been announced yet--and an immense ballroom will be on the second. Offices are will occupy the third through the 13th floors. The hotel and condominiums will occupy the top 10 floors.

Tenants in the new building will have spectacular views on all sides, situated as the building is in the middle of the Golden Triangle.

Mr. Saulson estimated that Reed Smith should be able to move in by next Memorial Day and PNC will do so by the end of 2009. The condominiums, being marketed by Howard Hanna, should be ready by 2009's close. The hotel should be ready for guests by late August or early September, he estimated.

He noted that the building can receive U.S. Green Building Council-established Leadership in Energy and Environmental Design, or LEED environment standards, in five areas--the building's core and shell, Reed Smith's space, PNC's space, the hotel and the condos.

PNC also plans to construct a public park in a triangular-shaped plot at the corner of Fifth and Liberty avenues in front of the building. It will include benches and drought-resistant plants and people will be encouraged to bring their dogs there.