7 facts about the Sydney harbour bridge

To celebrate the anniversary of the opening of the bridge, here are 7 facts about the Sydney landmark. Yes I know it opened on the 19th, but it's the 19th in Australia!

1. They had to paint it grey because there was no other colour of paint available in such large quantities taking 272 thousand litres of paint to get the first coat on.
2. The bridge wasn't paid off until 1988.
3. There are no nuts and bolts holding the bridge together, only 6 million rivets, the largest one weighing 3.5 kilos.
4. The pylons are only decoration! They don't really hold it up.
5. The arch rises and falls 18 centimetres due to heating or cooling.
6. 96 railway engines were parked on the bridge in 1932 to test its load carrying capacity.
7. It is the widest long-span bridge in the world.