This classic bit of '70s moie kitsch is a very, very wet pop fantasy designed to cash in on Olivia Newton John's popularity that cost $US13 million to make, flopped disastrously and ended her screen career. Gene Kelly apparently took the role because it was to be filmed close to where he lived. He should have stayed at home.
If you're into bad musicals, or just bad films, you'll have hit the jackpot with Xanadu. With excruciatingly lame acting (to use the world loosely), a large amount of it on roller-skates, truly awful costumes, make-up and production design and completely banal story line and dialogue (the script was written as the filming went along) the film inspired John Wilson to create the Razzie Awards, with director Greenwald winning the first ever Worst Director Award. The score by Jeff Lynne and ELO went on to chart success however.
FYI: If you like this then you should also consider, the Village People exploitation flick, Can't Stop The Music (1980) as a double bill of awfulness.