When we were in Hamburg a couple of weeks back we visited MiWuLa. That would be Miniature Wunderland - the world's largest model train world. We were there with my whole family - kids, parents, sisters and their kids - to celebrate my father's 60th birthday (which was last year already, but hey, there are only so many available weekends to match in a year...) My dad was in to trains when he was small (and still is), thus the visit.
It's a good spot for kids, although it is more fun for an adult; trying to find all the small fun, ironic details and scenes. For me it's not so much the trains (that actually go around the whole damn thing, all trough different settings and scenery that blend into one another in different etages, some 10km all in all, which itself is a total whoah -well, that's kind of the actual point with the whole place) but all the things happening.
Well there are quite a lot of accidents actually.
And the small green men and men in suits underneath area-51.
If you have a thing for technique, kitschy details, miniature stuff (and of course model trains) then you should definitely stop by MiWuLa when in Hamburg (and book tickets in advance to avoid waiting for hours).