The Johnson Space Center, Houston

Not a laugh-a-minute but a good day out. Presented as an education for kids, the tourist facilities take several hours to do and require some planning since various shows run for only a couple of times during the day and some clash. You get to see over the shoulders of 'real' NASA controllers if you go on the escorted tour of the working facilities there. But most of the show is in a tourist building which is so air-conditioned that you'll need an excellent constitution or long-sleeves. There is a space rocket outside (how do they stop it from rusting?) and it's fun browsing the themed merchandise before you leave. It attracts very small crowds considering its importance.