Metropolis
I remember watching this a couple years back, and it's the main reason I took a German Cinema course last semester.
It's just so beautiful and there's not much else I can say.
For the longest time I've admired 1920s Expressionism, and silent films, and so I know that if I'm ever able to make a film I would make it in the same vein as 1920s Expressionism, it would be silent, with the intertitles, and have all the film techniques used in 1920s cinema.
One thing I admire most is that they don't really use special effects, and yet, these films are some of the most beautiful that I've seen. The set designs are play-like, and over the top, yet feel more real than any film made nowadays.