This month the Sydney Harbour Bridge marks its 75th year. The structure, which took nine years to build, was declared open for traffic in March 1932 and remains to this day the world's largest steel arch bridge. Today more than 200,000 people took the rare opportunity to walk across a structure normally filled with traffic.
The bridge, which is known affectionately as the Coathanger, has 6m rivets in its 52,000 tonnes of steel. Today's celebrations also had a moment of commemoration - a plaque was unveiled to honour the 16 workers who died during its construction.
The bridge was finished in the Great Depression and was sometimes called the iron lung because it helped breathe life into a city and country experiencing terrible economic hardship.
The design of the bridge still arouses debate - both Australian engineer John Bradfield, who oversaw the project, and British consultant engineer, Ralph Freeman, are cited. Both are on the opening plaque.
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