The Dom comes to Hamburg three times a year. It's like a giant fair ...but more giant than you are thinking. It's huge.
I impressed that it leaves at all because it's HUGE. It must take forever to set up/take down.
It involves the worlds largest portable roller coaster. See, even dumb ole' wikipedia talks about it. http://en.wikipedia.org/wiki/Olympia_Looping Maybe next time I should go on it. :)