Burningman Festival in the Black Rock Desert of Northern Nevada since 1997.
It’s not billed as clothing optional but it’s…nudity is as accepted as it’s expected. The crowd this year will probably be about 50,000 people and during the day around http://zykad.com will be nude and around 60% will be at least partially naked. The percentage of nude people is higher in the early mornings before folks get into their costumes. Nude folks are entirely accepted and, really, not even discovered considerably as the costumes that so many people wear are so creative and amazing as is the giant artwork and fire-art that is what the occasion is really all about.
The event is not for everyone.
You camp in http://videonudism.com/hot for a week and everything you have to eat, drink and remain healthy and cozy has to be brought in by you…nothing except ice and java is for sale on the desert.
The people in our group bring some amazing costumes, as do most attendees, but we also go around nude when we are just seeing the artwork. Burningman is probably THE biggest mix of clothed and naked men and women on earth during the week it runs. (From 1 week prior to Labor Day to Labor Day.)