In 1973, Orson Welles narrated this animated short, which features somewhat surreal artwork by Dick Oden. You can see more of Oden's work here.
The Allegory of the Cave illustrates Plato's view of knowledge as presented in Book VII of The Republic: in ordinary experience, we see only shadows of the true world, which we can only behold by pursuing rigorous philosophical analysis.
This is not the only time "The Cave" has been set to film in some form. Open Culture readers may recall this brilliant version done with claymation. Gluttons for punishment may wish to peruse this collection of 20 YouTube versions at PartiallyExaminedLife.com, many of them frightfully amateurish and some of them presenting a warped and/or incomprehensible version of the story.
Mark Linsenmayer runs the Partially Examined Life philosophy podcast and blog, which recently released an episode discussing Plato's Republic.