The plan includes an extra 5000 square metres of exhibition space and a new storage facility, as well as renovated galleries, a children’s play space and extensive outdoor landscaping.

The museum has already amassed around $55 million in federal funding and has begun some of the works, including the $7.5 million children’s space, due to open next year.

Museum director Mathew Trinca says the plan will carry the 17-year-old site into the future, and will allow the museum to do its job.

“When you think about what is absorbing us now, as we look to reconcile 65,000 years of human history of this continent with the wonder of making modern Australia, the museum is at the very epicentre of that effort,” he said.

“That is our territory, about working across the breadth of Australian history, and making the connections between the key strands in our past. That's why we think over the next 12 years, we have ambition to grow our capacity. Not because we want to spend $266 million, but because we know these facilities are what's needed to take the museum to the next stage of its development, and properly realise its mission to tell the Australian story, to bring the Australian story alive.”

Mr Trinca said while the big-ticket items - the $104 million new exhibition space and the $100 million external collections centre - were yet to be funded, he was confident that the museum’s vision was strong enough to secure it in the future.

“A master plan is about vision for the future beyond the terms of government, as well, for the next 12 years, and that's why we say the master plan needs to show that our intention is to double the exhibition space for the national historical collection,” he said.

He said the recent announcement of $500 million in federal funding for expansions to the Australian War Memorial had convinced him that future governments would be supportive of the museum’s vision.

“What I think the War Memorial has shown is when you get the narrative right, when you show the breadth of your ambition and what you can do for the public, then governments are prepared to support those good ideas,” he said.

The new exhibition space, the Theatre of Things, appears in the master plan as a futuristic glass-and-metal dome alongside the original building.

It has been designed by the same architects as the controversial 17-year-old building, Howard Raggatt of Ashton Raggatt McDougall.

“ARM's work is all about referencing earlier works in Australian life, but reinventing them in design that really speaks to the future,” Mr Trinca said.

“That's what this site should be - it's a jewel in Canberra's crown, the Acton Peninsula, and we should continue to look for the very best, the most inventive architecture we can to make this a site that's a destination in its own right.”

But he also revealed that he had been in talks with the director of the National Film and Sound Archive, Jan Muller, who announced earlier this year that the archive was looking for alternative accommodation, having outgrown the heritage building that once housed the Museum of Anatomy and Canberra’s first morgue.

Mr Trinca said a site further down the Acton Peninsula had been mooted as a possible site for a new archive, and that he was open to the idea of combining a new exhibition space.

“If we did that, we'd be bringing our collection into dialogue with their extraordinary audio-visual collections in the same facility,” he said.

“It's early days on that at this stage, but that's one way would deliver on this ambition.”

He was also hoping that plans for a new $100 million centre for museum collections, on a greenfield site in addition to its current storage facility in Mitchell, would involve other institutions.

“Ideally I'd like to think that that becomes a collaborative project with some of the other institutions,” he said.

“I have some hopes for the idea that some of the cultural institutions that face similar problems will band together to deliver those kinds of collection storage solutions in a shared area.”

The master plan also includes a futuristic boathouse for the Enterprise paddle steamer, that forms part of the museum’s collection but is not protected from the elements.

The new boathouse, which would extend into the lake, would also include a museum to “celebrate technology from steam through to renewables and look at its impact on Australian society”.

This addition, scheduled for completion in 2021, would cost around $12 million, and would potentially be partly privately funded.

There will also be extensive redesigns of the central Garden of Australian Dreams in 2025, and a lakeside plaza to take advantage of the land behind the museum that is currently used as a service entrance.

“$265 million is a lot of money, even over 12 years,” he said.

“We think it will transform the museum and take it to the next level. This is what the nation needs, because this is the only place where the expansiveness of the Australian story comes together, those different strands come together in one institution.”