One thing won't change in war memorial overhaul

The haunting silhouette of the Australian War Memorial's dome has endured for decades beneath Canberra's Mount Ainslie.

Nestled in front of the bushy landscape, it serves as a striking reminder of sacrifice - and it's not about to change even with the memorial's $500 million development.

The war memorial has affirmed its decision to retain the dome's integrity and, for the first time in decades, given the public a look inside its top.

Memorial director Matt Anderson said of the dome "you can't improve on perfection" while facilities manager Jana Johnson describes it as an icon. 

"(It's) the silhouette that you see across Canberra," she said. 

"The heritage building itself is not being impacted by the construction works.

"Everything that you see here is going to remain intact and we do everything to ensure that we protect and preserve the heritage building."

The top of the dome is usually only accessible to people working to maintain the building or check on its condition.

Images of inside the dome reveal ladders and more than nine winding flights of stairs leading to its top, along with windows shining through the darkness, and the steel beams and timber that support it.

A single light fitting glows down onto the tomb of the unknown Australian soldier through a mosaic above the Hall of Memory.

"Within the mosaic you see a tiny light which is representative of the sun, which illuminates the tomb," Ms Johnson said.

The mosaic depicts souls of the dead rising towards their spiritual home.

The hall is the most sacred place at the memorial, and the light shines 24 metres down to the tomb, Ms Johnson said.

The dome was originally envisaged to be clad in terracotta tiles but years later, it was thought cheaper to clad in copper.

The material was expected to naturally weather in Canberra's conditions, however there wasn't enough pollution to have it naturally oxidise, Ms Johnson said.

It's said that the decision was then made in the early 1950s to oxidise it with chemicals to turn it green.

War memorial staff still don't know much about the soldier that lies in the tomb beneath the dome - a deliberate move, according to official records curator Stuart Bennington.

The soldier was selected from four bodies at a grave in France and interred in the hall in 1993.

"The whole intention was that it loses the meaning if you actually know who the soldier is because they're meant to represent all those who never had a name grave," Mr Bennington said.

"We do occasionally have people ask us, 'Have you tried DNA testing and that', but we won't do that, because it defeats the purpose."

The dome is in its original condition aside from a few minor upgrades including lights and windows, Ms Johnson said. It was built in 1940.