What is "fruhlingsfeier"

"Frühlingsfeier" (English Spring Festival, or Rite of Spring) is a song composed by Richard Strauss using the text of a poem with the same name by Heinrich Heine (1797-1856), the fifth in his Opus 56 collection, (TrV 220) which was published in 1906. Originally written for piano and voice, Strauss wrote an orchestral version in 1933.