On Sunday 25 October 2009 the Sydney Harbour Bridge was closed to traffic for the morning to hold a massive picnic. The event was organised by the NSW government as part of their spring festival. Just 6,000 people were chosen by lottery to join the picnic.
The ABC news site (where I got the picture) gives a short report and an excellent time lapse video showing from start to finish.
Although just a small event the message this sort of event sends out is great - the car is not king, roads can be closed for people.