Three d is of course the venture which started in the 1960s with stupid glasses, and that domed shaped thing called Cinema 2000, which appeared to be needed to be situated in a large muddy field while a panoramic image of a rollercoaster was shown, making people lean etc and humour ensuing when one of them fell in the mud.

Like the previous post, this highlights the imagination - and ot some extent maths - involved in actually making a pattern on the walls and ceiling which could be three D, but isn't. More here.