At the Museum Of Science And Industry in Chicago. Last of its kind in existence, and has a nice display of all the artifacts relating to it. I haven't seen it since I was a boy.

If you are on Merseyside, go and see the sectioned U-Boat near Birkenhead. It used to be in one piece, but they have now, for safelty reasons (bah!) cut it up and put perspex panels on each piece. You can see most of the original fittings and there is a museum attached.