Although I never got the chance to attend one during my "scout career", since it's held only once every 4th year (yes, exactly like Football World Champions Ship, or the Olympic Games), and you have to be, correct me if I'm wrong, between 15 and 18 years old.
Anyhow, their website is very complete; you can follow the camp online with their webcams and blogs and for the 39.000 participants, in order to find their way around there's of course an application that helps you get around the camp (hope this isn't working when it's time for the orientation competition), in my days we could only dream of these kind of things!^^
Ten years ago I attended a National Jamboree in the exact same spot, with mostly Swedish, but also quite some international scouts; Scout 2001, with 26.000 participants. If you're curious about what scouting is all about, these gigantic camps are definitely something to visit!
All photos are from the open Facebook group "Jag var på Scout 2001
Believe this photo speaks for itself
The big stage
"Home made" ferries wheel (doesn't it look just like a Flintstone's invention?)