Apart from being a great excuse for some fun, fun, fun in the sun, sun, sun, this annual event has a serious purpose in protesting against oil dependency and car culture. It celebrates both the versatility of the bicycle and the diversity and beauty of the human body - while offering a stark reminder of the vulnerability of the cyclist in modern traffic.
Now in it's eighth year, it involves thousands of riders in 50 cities worldwide. You can see the 2013 UK schedule and read more about the event here. The riders usually circle our streets for 40 minutes or so. Fancy dress and body paint are optional - helmets and knee pads are probably a must.
So go along and support it ( you know you really want to ). Take a pad and some charcoal - but you'll have to sketch fast !