This is not my personal opinion (I prefer F. W. Murnau's FAUST) but it is the general consensus regarding this groundbreaking adult film which made a screen icon out of Louise Brooks and assured G.W. Pabst his place in cinema history. The movie is based on two plays (EARTH SPIRIT and PANDORA'S BOX) by controversial German playwright Frank Wedekind who wrote them at the dawn of the 20th Century with the deliberate intent of shocking his middle class audience by talking bluntly about the consequences of sex, violence, and hypocrisy. Austrian composer Alban Berg would later use them as the source of his unfinished opera LULU.
G.W. Pabst already had a reputation as a director of German neo-realism thanks to the 1925 Greta Garbo film THE JOYLESS STREET (influenced by D.W. Griffith's ISN'T LIFE WONDERFUL of 1924). In the sound era he would make the film version of THE THREEPENNY OPERA (1931). PANDORA'S BOX mixes realism and German expressionism in equal amounts to tell the story of a naive dancer/prostitute and the tragedy she brings to everyone who tries to become close to her. It's amazing how Pabst saw something in Louise Brooks that no one else did and then brought it out so effectively onscreen. From the performances to the lighting, the editing and the camerawork, to the relentlessly downbeat mood, PANDORA'S BOX is a true landmark of the cinema (silent and sound) that anyone seriously interested in film should experience.
Finally available in the U.S. on DVD, this Criterion 2 disc set is all that you could ask for. The print for its age (1928) looks great and you get the choice of 4 different background scores which show how important music is to silent cinema. Each one makes it a different viewing experience. My personal favorite is Peer Ruben's modern orchestral score although you also get classical, cabaret, and piano to choose from. It also comes with 2 documentaries on Louise Brooks, informed commentary, and a 90 page booklet. Now that's the way to treat a cinema classic!