Parsifal
Parsifal is an opera in three acts by Richard Wagner.  Wagner took most of the story from a medieval poem Parzival by the German poet Wolfram von Eschenbach.  It was the last opera that Wagner completed.  He started thinking about it in 1857 but did not do much work to it until after he had finished the cycle of four operas known as the Ring Cycle which was produced complete in 1876 in the special theatre (Festspielhaus) he had built in Bayreuth.  Wagner composed his opera Parsifal so that it would suit the sound of this new theatre.  It was first produced in 1882.  The story is related to the Arthurian legends.