It's been lit up in dazzling colour, crossed by elephants, scaled, photographed, picnicked and paraded on, and sailed under.

Sydney's iconic Harbour Bridge has been the centre of more activity and hubbub than most other structures around the world.

Now it's being celebrated.

The Coathanger, as it is affectionately known, is celebrating its 80th birthday.

A special 1930s-themed picnic party will be held this Sunday at Bradfield Park to mark the 80th anniversary of its opening on 19 March 1932.

NSW Roads Minister Duncan Gay says the event - held between 9.30am and 2pm - includes historic displays, vintage fashion parades, big bands and roving entertainment.

"Several special guests with links to the bridge will also attend the day to share their stories about the structure," he says.

The Sydney Harbour Bridge - 1149m long including the 503m arch - is listed in the Guinness Book of Records as the world's widest long-span bridge.

It took almost 10 years to build and cost 6.25 million pounds.

After many false starts and countless re-designs, work began on the Dr John Job Crew Bradfield-designed structure in July 1923.

More than 800 buildings in the Rocks and North Sydney were demolished to make way for the structure.

Construction involved 1400 workers, 52,800 tonnes of steel, 6 million rivets weighing 3200 tonnes and 95,000 cubic metres of concrete.

And 272,000 litres of paint were used in the first three coats on the bridge.

It was officially opened on March 19, 1932 and just a few weeks later six circus elephants crossed the bridge at a cost of two pence a head.

Upon opening, some 11,000 vehicles crossed the bridge every day. Now 160,000 vehicles each day make the journey.

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