Skytower, nearing completion at 222 Margaret Street, is so big it can house the entire population of Longreach.

Skytower soars to the city’s tallest allowable height of 274 metres, with construction set to wrap up by June.

The ear-popping elevator ride to the 90th floor takes almost two minutes, where construction is almost complete on what the developers claim is the highest infinity pool on Earth.

Tradies working on the bellwether building spend their lunch hour towering over the city and enjoying the views from a height that dwarfs surrounding skyscrapers and reduces trucks to the size of ants.

As the builders polish off their packed lunches – and if the haze abates – they say they can catch a glimpse of Stradbroke Island's sand dunes or the Gold Coast's skyline.

Sydney-based property developer Billbergia, investment company AMP Capital and Hutchinson Builders are behind the project, nicknamed the "Christmas bon-bon" for its three distinct sections.

About 650 apartments in the bottom two thirds are now occupied, while builders work to finish the top section by June.

At the top of each section is a pool, gym and streamroom, but only occupants in the top section will have access to the infinity pool.

Ten years ago, the plan for the Margaret Street site looked very different.

The "Vision Tower" was slated to win the race to be Brisbane's tallest building – until the global financial crisis and the site was sold off to Billbergia.

Vision was to be a curved, 283-metre skyscraper with an observation deck, 13 floors of commercial space and 376 residential apartments over 72 floors.

Construction on Vision did not pass the excavation stage. The resulting huge hole in the ground sat dormant after developer Austcorp went into receivership in 2009 and famously filled up with water during the Brisbane flood of 2011.

Brisbane City Council gave the green light for Skytower to go ahead in 2014 after years of false starts, and construction kicked off the following year.

The tower has been settled in stages in order for the senior debt to be paid down and to avoid the chaos of 3000 people moving in at the same time.

Billbergia spokesman Rick Graf said the exclusive top eight floors, filled with penthouses, had not yet been released to market but were expected to go on sale by the end of the year.

The largest penthouse was expected to sell for about $8 million, though Mr Graf played coy on the value of the apartment, which spans three levels.

"It is not only a large building, but it is refined, elegant and beautifully finished," he said.

"When everyone gets a chance to walk through the main foyer later this year, they will be very impressed."

Mr Graf said about 90 per cent of the 900 apartments already sold were snapped up by Australian buyers, many from south-east Queensland.

The Australian Financial Review reported some owners discounted apartments by up to 10 per cent to make a sale.

Apartment 1316 of Skytower was purchased off the plan for $696,960 in 2015 and sold by owner Hyoung Suk Kwon for $608,880.

While Skytower was the first to reach Brisbane's height ceiling, it will not be the last.

Five other buildings have received Brisbane City Council approval to reach the aviation-enforced 274-metre limit.

155 Edward Street

Aria Property Group was approved to build an 82-storey gold-coloured tower on the corner of Edward and Elizabeth streets, near St Stephen's Catholic Cathedral.

300 George Street (The One)

The 82-storey residential tower is part of the $800 million Brisbane Quarter at the old law courts on George Street. The One will sit alongside a 39-storey office building and the 32-storey W Brisbane Hotel.

217 George Street (No.1 Brisbane)

No. 1 Brisbane will tower above Brisbane's busy Queen Street Mall and plans promised the skyscraper to include a bar, retail and a public entertainment space.

240 Margaret Street

This 91-storey skyscraper will neighbour the "Christmas bon-bon" on Margaret Street and will include 783 units.

30 Albert Street

Singapore-based developer Aspial, which also bought the site at 240 Margaret Street, is constructing a “vertical community” with elevated gardens on Albert Street.

The six towers touching the city limits are part of a massive growth across Brisbane's CBD which are set to transform the Queensland capital by 2022.

Lord mayor Graham Quirk said Brisbane was a growing city with about 50 CBD skyscrapers expected to be built over the coming 20 years, to accommodate the demand for commercial and residential growth.

“More people are living in the Brisbane CBD than ever before and by 2031 an additional 80,000 employees will be working in the city centre,” he said.

“Brisbane’s CBD skyline has the potential to accommodate buildings of a greater height than the current maximum of 274 metres and it is important that we have a broader discussion about this opportunity, to avoid missing out on economic investment and local jobs.

Cr Quirk said there was still a "clear interest from industry to go higher".

“With aviation safety as a clear priority, we should still be able to have areas of the city where we might be able to go to 300 metres to provide some flexibility in the medium-term," he said.

“I want to ensure we protect our city's strong aviation safety record but I think we should have a sensible conversation around flight paths and future technological changes in aviation that may create the potential for, if not all, some parts of the city to at least be able to go higher.”