If you're like me (which isn't likely) you've often wondered "how big is an Imperial Star Destroyer compared to, say, a 747, or the Stay-Puff Marshmallow Man?" Even if the thought had never crossed your mind, this is still a good and valid question. I've been to the top of the Eiffel Tower, and now I know the relative size of the big ship in Close Encounters. Check out this site for the comparative sizes of all sorts of sci-fi craft and Earthly structures.