Australia's most instantly recognisable landmark is also its most contentious building, and once again the Sydney Opera House is at the centre of a vigorous debate - this time over the cost of preserving it for future generations.
It is a building of multiple entendres. Looking up from harbour-level, it brings to mind the billowing spinnakers of a flotilla of racing yachts.
In side profile, a bowl of razor-edged oyster shells. Through the shrubbery of the neighbouring botanical gardens, the tips of its elliptical shells look like the unhatched eggs of some giant, prehistoric beast.
Because you can view it in so many different ways, the Opera House seems an especially fitting icon for post-war Australia.
Back in the mid-1950s, the New South Wales government decided to mount an international competition, which was eventually won by a relatively unknown Danish architect, Jorn Utzon.
But he was sacked well before the completion of his masterpiece, and its interior was finished by a local architect.
The Opera House was built with the help of a lot of new arrivals from southern Europe, which speak of the demographic changes which overtook Australia after the war.
It was opened by Queen Elizabeth II - a reminder of the enduring constitutional link with Britain, and was funded with the help of lottery money (a reminder of the popularity of gambling).
The stage trap where Don Giovanni comes through is directly above the timpani - not very comfortable
Richard Evans Sydney Opera House
Now this treasured national icon is once again in the spotlight, as the Sydney Opera House tries to secure funding for what it says are much-needed renovations.
The backstage equipment is in a state of dilapidation, and the orchestra pit is so small and acoustically compromised that players have to work in rotas to safeguard their hearing.
The stage is so narrow that stage hands have to wait in the wings to catch the ballet dancers as they hurtle off stage.
Richard Evans, chief executive officer of the Sydney Opera House, showed me the cramped conditions in the orchestra pit.
"This is the percussion section, they can't even see the conductor, so they have to look at the conductor through television monitors."
There are other idiosyncrasies, he says, including the stage traps directly above the musicians' heads.
"The stage trap where Don Giovanni comes through is directly above the timpani. Not very comfortable."
In the bowels of the building he showed me the stage equipment which has been going flat out virtually every day for the last 35 years.
"Do you know what? It's coming to the end of its useful life and sometimes it breaks", he explains. "When this stops, everything stops.'"
Architect Jorn Utzon died last year at the age of 90
Then there is that gnawing problem of what to do with the entire interior, which has always been a colossal disappointment - as forgettable as the exterior is memorable.
Utzon had wanted the inside of the Opera House to be distinct from his monochromatic shells. He envisaged a burst of sub-aqua colour, with a palette drawn from the underwater world.
But he was removed from the project in a row over mounting costs and left Australia, never to return.
If the building is shut down to complete the backstage renovations, then the Opera House feels it makes sense to try to realise aspects of Utzon's vision all in one go.
This is a once-in-a-century chance to get it right.
The problem, as it was in the Sixties, is the cost. The Sydney Opera House estimates it at A$600 million (£300 million).
Prime Minister Kevin Rudd has already balked at that price tag, saying the money should be spent elsewhere, with hospitals in more urgent need.
Certainly, if you frame the financial argument in terms of opera-goers against sick patients, then most Prime Ministers would come down on the same side.
But supporters of the improvements would argue it is a false choice. And cannot Australia afford both?
Since Jorn Utzon died last year, many have argued that the most fitting memorial would be to realise his vision. But this is a building which seems to defy consensus and not everyone agrees.
Elizabeth Farrelly, an architectural critic who writes for the Sydney Morning Herald, questions the wisdom of the project.
'I think what you don't do when you have a national symbol is go back and fix it up. You don't go back and fix up the Eiffel Tower and I don't think we need to fix up the Opera House.
"One thing the Opera House doesn't do, and will probably never do, is accommodate full-scale opera.
"That's a wonderful irony about the building, but something that you can love. Probably a better option is to build a new opera house somewhere else," she says.
Putting right this national icon has not yet become a national priority, nor a matter of national consensus.
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