Sydney Harbour Bridge 75th anniversary

The Sydney Harbour Bridge celebrates its 75th anniversary today, March 19. Construction started on the granite pillars 1923 while work on the steel arch started in 1929. The arch spans 509m (1,559 feet) and weighs 39,000 tons. The top is 134m (415.4 feet) above sea level, although the height can increase by up to 180mm (7 in) on hot days as the steel expands. Photograph: OTTTO Holdings

Designed to carry road traffic, trains and trams, the bridge opened on March 19 1932. Sixteen men died while working on its construction. At a total cost of £10,057, 170.7s.9d, it cost twice as much as the original estimate – it took until 1988 to finish paying off the loans. Photograph: OTTTO Holdings

The official opening day of the bridge drew large crowds. Photograph: OTTTO Holdings

Now one of the most iconic bridges in the world, Sydney Harbour Bridge spans Sydney Harbour, joining north and south Sydney. This view looks east, towards the Pacific – the opera house and the city’s financial district are on the right. Photograph: OTTTO Holdings

The bridge has been open to tourists since 1998. Tours run all day, from dawn to dusk and are only cancelled for electrical storms or high wind. Climbs start on the eastern side of the bridge and ascend to the top. At the summit, the group crosses to the western side of the arch for the descent. Photograph: OTTTO Holdings

Looking down from the centre of the bridge. Six lanes of traffic can’t accommodate all of Sydney cross-harbour traffic – a tunnel was opened in 1992 to ease congestion on the bridge. Photograph: OTTTO Holdings

Sunrise greets early-morning climbers on top of the bridge. Photograph: OTTTO Holdings