The ACT Planning and Land Authority has given the green light to the construction giant's plans to redevelop land on Cooyong Street, opposite Glebe Park.

The project will include construction of three distinct mixed-use buildings, ranging in height from five to 12 storeys.

The so-called Metropol tower, which Geocon has declared the precinct's centrepiece, will include 280 apartments and more than 2000 square metres of commercial space. The Tryst development features 160 apartments, while the precinct's Envie building includes 80 units.

The three buildings have been designed by Fender Katsalidis Architects, whose portfolio includes the MONA art gallery in Hobart and Nishi complex in New Acton.

Construction work is scheduled to start on June 30 and be completed by mid-2021.

Buyers have already snapped up 400 of 520 units on offer, which Geocon said was evidence of an "insatiable appetite in Canberra for trendy inner-city living". The two, $2 million penthouse apartments at Envie, the most high-end of the three buildings, have already sold.

The authority's decision comes almost 18 months after the construction giant first presented its vision for the Reid site to the ACT government's National Capital Design Review Panel.

It had four meetings with the panel before lodging a development application with the planning authority in June 2018.

A total of 13 submissions were received during a public consultation window, with respondents' concerns ranging from a perceived lack of prior community consultation; to apartment size and the potential for overshadowing of nearby Argyle Square.

Brett Phillips, a deputy director general at the ACT government's planning and development directorate, said the authority had asked Geocon to reconfigure a proposed basement carpark in order to protect registered trees.

Mr Phillips said the authority was ultimately satisfied that the development complied with the territory plan, which encouraged high-rise developments on the prime inner-city site.

The Geocon development will rise up next to JWLand's Founders Lane precinct, which will include 700 apartments once complete.

The authority has attached a number of conditions to the approval, including that the registered trees be protected.

It has also warned Geocon that any proposed tweaks to the building's design could be subject to further rounds of public consultation.

Geocon founder and managing director Nick Georgalis welcomed the approval of his signature inner-city project.

"We fought hard to have this opportunity, to create beautiful new buildings for future generations to enjoy in such an iconic part of Canberra," Mr Georgalis said.

"We have paid careful consideration to Canberra's most-historic, architectural forms while also presenting a glimpse into the city's future.

"I'm confident Canberrans will love these buildings as much as I do."

The Cooyong Street precinct is part of Geocon's ever-expanding suite of projects, which includes developments in every town centre.

The company has recently added two more projects to its portfolio after it entered into joint ventures with developer Empire Global.