It's one of Auckland's most loved buildings, iconic in the true sense of the word. And after 12 years of restoration and additions, the Auckland War Memorial Museum is months away from a historic transformation.

From the exterior, the undulating copper and glass dome at the rear of the museum is the most visible sign of the final, $64.5 million grand atrium filling in the central courtyard with a huge suspended four-storey bowl clad in rough-sawn Fijian kauri - from a sustainable forest, naturally.

Inside the new rear entrance, where a generous lobby leads to an exhibition hall the size of five tennis courts, 200 contractors and subbies are scurrying like ants to meet the December 8 opening deadline. A matrix of scaffolding fills the atrium, where light will descend through the glass-edged dome down four storeys to the volcanic basalt floor.

After all, the treasure trove of five million objects is sitting on top of a dormant volcanic crater, known to Maori as Pukekawa, the first to erupt on the Auckland isthmus 55,000 to 140,000 years ago.

Museum director Rodney Wilson is not wrong when he says the project is no normal office tower.

The four-storey bowl, suspended from four pillars serving as lifts, houses a learning centre, 200-seat theatre and an events centre with seating for 450, providing an almost 360- degree view of the city and harbour. There will be access from the events centre to the rooftop.

"It is going to be absolutely astonishing. You can already see the effect of the dome from the exterior and it sits beautifully on to the building," says Dr Wilson.

"People keep talking about an iconic or landmark building we need to build in Auckland, but sometimes we forget that we have got one or two and this project is about adding to one of those buildings in a sympathetic and appropriate way."

Work updating the museum building began in 1994 and stage one, the restoration of the original 1929 building and replacement of exhibits, was completed in 1999 for $43 million.

The grand atrium project started in December 2003, coinciding with a building boom and soaring costs for steel, glass and copper that boosted the price from $48.6 million to $64.5 million.

The Government ($27 million) and ASB Trusts ($12.9 million) were the largest donors.

The project will open with an exhibition telling the story of the last migration of humans down through the Pacific.