"Music is liquid architecture; architecture is frozen music," according to German writer Johann Wolfgang von Goethe. He wasn't referring to the Sydney Opera House, of course, but if he had been born in 1949 instead of 1749, he could well have been.

The sculptural tour de force that has become not only a symbol of the emerald city itself, but of Australia as a whole, turns 40 today. On October 20, 1973, Queen Elizabeth II declared the opera house open, before taking a seat for a performance of Beethoven's 9th symphony, played by the Sydney Symphony Orchestra.

Next Sunday, the same symphony will ring out across the forecourt in a twilight anniversary concert featuring soloists from Opera Australia and the Sydney Philharmonia Choirs. The concert will be attended by Crown Prince Frederik and Crown Princess Mary of Denmark.

It was a Danish architect, Jorn Utzon, who, in 1957, won the competition to design an opera house on Sydney's Bennelong Point. The story goes that one of the judges, Eero Saarinen, spotted entry No218 in a pile of already rejected designs and declared it the winner. The rest, as they say, is history.

In truth, the story of how the landmark got built is a long and bitterly political one that saw Utzon resign from the project following an argument with the New South Wales government over money to pay his staff and for the plywood prototypes of the interiors. It would be another seven years - taking the project a decade past its original projected completion date - and a cost blowout to A$102 million (the original estimate had been A$7 million) - before the opera house would be ready to host its first performance.

Over the years since, it has hosted some of the world's top talent. Everyone from Frank Sinatra and Luciano Pavarotti to Sting and the Foo Fighters have performed on its hallowed stages. However, it was American singer Paul Robeson who can be credited with the first performance by an international star; in 1960, when the opera house was still a construction site, he bellowed out a stirring rendition of Ol' Man River to the labourers during a lunch break.

Almost 50 million people have attended a performance at the opera house since its opening and it is visited annually by a further 8.2 million.

In 2007, the opera house was inscribed on the World Heritage List. The expert evaluation report to the World Heritage Committee stated: "… it stands by itself as one of the indisputable masterpieces of human creativity, not only in the 20th century but in the history of humankind."

If you really want to see what makes the opera house such a special place, you could join the 320,000 who take a guided tour each year. Most folks opt for the one-hour Sydney Opera House Tour, which runs daily. This can be combined with a three-tier tasting plate (as lunch or dinner) from the nearby Opera Kitchen.

Alternatively, do as we do and take the Backstage Tour, which gets you right into the bowels of the building, through a labyrinth of corridors and rooms. The tour kicks off daily at 7am (to ensure access to most of the theatres) and concludes with a breakfast in the performers' private Green Room.

The centre of the building is a thoroughfare for semi-trailers bringing equipment into the house. It is a hive of activity, with lots of crates, forklifts and blokes in fluoro vests, and a world away from the elegant scenes set upstairs.

Our guide, Yvonne, leads the way to the cavernous scenery dock, where sets and scenery are stored before being lifted up to the main stage of the opera theatre. Because the opera house has no wings at the sides, everything that appears on stage, including the performers, must come up from below, via lifts and stairs.

"Over the years, this scenery dock has hosted some pretty special parties," says Yvonne. "The Australian Ballet lined it with red velvet and hung a chandelier from the ceiling for one of their gatherings. The late John Denver filled it with table tennis tables to keep his crew entertained."

Next we go upstairs to the orchestra pit, where we are invited to stand on the podium and hold a conductor's baton for a photo op, before being led around to the dressing rooms of the stars.

One of the biggest ever to grace the stage of the opera house was La Stupenda herself, Dame Joan Sutherland. The dramatic coloratura soprano was described as the "voice of the century" by Pavarotti (no slouch himself when it came to belting out a tune). She passed away in 2010 and her favourite dressing room here has been named in her honour. According to Yvonne, however, in the latter part of her career, Sutherland often got changed in the props lift, to save her returning to her room.

There are more than 60 dressing rooms throughout the opera house, with the stars getting the ones with water views. We get to peek into the dressing room of a rising star. It offers a wonderful vignette: a pair of patent leather shoes in the corner, an apple with a bite out of it on a coffee table, a bottle of contact-lens cleaner and a wilting box of roses.

There's also a Steinway grand piano in the room. There are 28 pianos throughout the opera house and a dedicated piano-tuner works his way around them.

An aircraft and some palm trees dominate the backstage area of the opera theatre. These are some of the props from Opera Australia's latest production: South Pacific.

The Concert Hall, beneath the largest of the iconic shells, dominates the western side of the building. Everything about the hall is gargantuan; from the 10,000-plus pipe organ that took a decade to build and two years to tune, to the giant diamond ring Sammy Davis Jnr once left sparkling on his piano following a performance.

"I love this building, it's so unique, it's almost like it's a living thing," says Yvonne, one of 70 guides employed. And she has heard it all; from the Japanese tourist who asked, "Does the prime minister live here?", to the American who inquired whether the building has a swimming pool.

"I told him it has a big pool right around the outside we call the harbour," she laughs.


Facts & figure

  • Construction work started in 1959 and involved 10,000 workers.
  • The highest roof shell, or sail. is 67 metres above sea level, equivalent to the top of a 22-storey building.
  • In 1980, Arnold Schwarzenegger won his final Mr Olympia bodybuilding title in the Concert Hall.
  • There are 1,056,006 ceramic roof tiles; a Sydney shower is usually enough to keep them clean and glistening.
  • The roof vaults weigh a staggering 158,000 tonnes and use more than four times the amount of steel used in the long arch of the Sydney Harbour Bridge. Stephen Lacey