He was a self-described naysayer and didn't think it was an exciting idea. But now he is its biggest fan.

"I guess I didn't think it was architecture. I just thought it was a tree thing. You know, we'd lost a few trees so 'Let's build some back'," Mr Trobe said.

"I didn't want an arboretum, really ... I didn't realise it would be such a well thought-out, bold, conceptual idea."

Mr Trobe said he loved how "beautifully organised" the arboretum was. He praised the composition of the built design - the Village Centre and the Margaret Whitlam Pavilion - with the natural design of the trees and rolling hills.

"The reason I like it is it's got very simple, geometric, environmental buildings and it's also fairly iconic," he said.

"Cities need buildings or attractions that draw them to it.

"Other cities have made their reputation by having a particular building."

The architects of the arboretum were chosen by a competition. It was designed by Taylor Cullity Lethlean Landscape Architects and Tonkin Zulaikha Greer Architects.

Mr Trobe said Canberra needed more bold buildings and concepts like the National Arboretum, he said there was a desperate need for more iconic buildings in the nation's capital.

"Canberra could do well by building iconic buildings, it already has some but something like the Sydney Opera House that is world-challenging and world-leading brings people to Canberra," he said.

"We've got the space, we've got the energy and we've got the newness to do that."

Mr Trobe said Canberra's growth was evident as more people were coming to the nation's capital out of choice.

"I think Canberra is emerging from adolescence into some sort of young adulthood and I think a lot of people are coming to Canberra now out of choice and lifestyle, rather than years ago people were complaining they had to come to Canberra because they were posted here," he said.

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But he said town planners needed to turn their attention to Civic. Mr Trobe was a big fan of the city-to-the-lake project and said the area would benefit from more public recreational buildings such as a stadium and a new convention centre. He feared development had pushed too far north.

"I think that bold notion of the city sliding northwards instead of more to the lake is a mistake," he said.

Mr Trobe said the lake should be held in higher regard as a focal point of the city.

"We have this fantastic resource ... it's brilliant but it's sliced in half by Parkes Way and there is no connection," he said.

"Any other big city would see that as a beautiful natural resource like Central Park in New York or Hyde Park in London ... we seem to have just emasculated our best feature from the centre of our town."