The Cabinet of Dr. Caligari directed by Robert Wiene is one of the most earliest films I have seen and a typical silent movie as the performers and set are theatrical so the actors perform with dramatic emotions and movement jestures to react with the scene space around them to describe what is going on. The plot was confusing and the sets reflect a horror nightmare with the mental asylum and killer.C J Brooks from http://www.wildsound-filmmaking-feedback-events.com/the_cabinet_of_dr_caligari.html sums the film up nicely "The caricatured sets, the distorted faces, the exaggerated shadows; the dour disposition: all lend itself to a brew of surrealism and fantasy."
Sets are paintings and stage props so has a school set production feel. The expressionist painting style captured the confusion nightmare theme. The use of the curtain to enter the cabinet was clever because it looked like a circus tent. Donald J. Levit from http://www.rottentomatoes.com/m/1003361-cabinet_of_dr_caligari/ gives an interestingly similar view "Even if taken as social or Freudian statement, Caligari's real star attraction is in the visuals."