If you've been to a performance at the opera house you may think you know the place but unless you've had a tour behind the scenes you've only seen the tip of the iceberg.
A guide will take you backstage, beneath the stage, down into the orchestra pit, allow a peep into the Green Room where you'll quite possibly recognise a celebrity or two taking breakfast, and you may even get centre-stage where the temptation to take a bow for an imaginary standing ovation is irresistible.
Along the way you'll learn that 1700 performances are given here every year and if you count conferences and other events inside and outside, the total jumps to 2400.
That's made possible by the fact that the sail-like rooftops cover not just an opera theatre but also a concert hall, a drama theatre, a playhouse room, and two smaller studio performance rooms, including the intimate Utzon Room, named after Jorn Utzon, the opera house's architect.
Utzon was little-known when he entered the worldwide competition in 1956 to design a concert hall and opera house for Sydney. His design - Submission 218 - arrived from Denmark just before the closing date but was added to the discard pile by the judging panel until a late-arriving judge retrieved it.
Although Utzon had never been to Australia, he was able to get a feel for the lay of the land and its views by studying maps and photographs, and his vision was chosen.
The bulldozers rolled on to the site in 1959 with construction expected to take three years. It took 14.
The original price tag was A$7 million. By the time the building was officially opened by the Queen on October 20, 1973, it had blown out to A$102 million.
The house's vital statistics are mind-blowing: for instance, it contains four times the amount of steel than the main arch of the nearby Sydney Harbour Bridge.
The design problems were vast: 16 schemes for constructing the roof shells were tried and rejected.
And, while the house is a success story today, early on the controversy was enormous: Utzon left the project in the mid-60s after scandals about cost overruns - Government-appointed architects saw the building through to completion - and although he was re-engaged in 1999 to develop a set of on-going design principles he never returned to see the completed Opera House.
Today, the Sydney Opera House is a A$100 million business ($127 million): A$30 million of that is purely for maintenance, the rest is operational costs.
The chief executive - New Zealand-born Richard Evans - says the house is the largest theatrical promoter in the Southern Hemisphere, bringing more than A$304 million a year into the New South Wales economy.
"The big thing we're concentrating on now is a digital strategy to broadcast live to movie screens in parks, televisions, computer screens, the shows and events that are happening right here in the house," he says. "It's a way to give people an Opera House experience off-site and online when they cannot get to Sydney."
Listed as a World Heritage List building, the house is often described as one of the architectural wonders of the world.
It's a magnificent structure ... but how sad that Utzon died late last year, aged 90, at his home in Denmark without ever being able to enjoy a performance.
Getting There
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