If you have never seen a silent film, I beg you to start with Fritz Lang's Metropolis which was released Jan. 10, 1927 in Germany.
In a futuristic city sharply divided between the working class and the city planners, the son of the city's mastermind falls in love with a working class prophet who predicts the coming of a savior to mediate their differences.
Considered by some to be an early precursor of steampunk, it is visually stunning - especially for the times. (While theoretically set in "the future" you can see 1920s cars in it - oops.)
The sci-fi epic ran an estimated 153 minutes when it was first screened in Berlin but by the time it debuted in the United States later that year the film ran approximately 90 minutes. (Exact running times are difficult to determine because silent films were not always projected at a standardized speed).
Metropolis went on to become one of the cornerstones of science fiction cinema foreshadowing Blade Runner and The Matrix.
Most of what was cut was thought to be permanently lost or destroyed although small segments were found over the years. However, a copy was discovered in 2008 in Argentina that included 25 minutes of "lost" footage, about a fifth of the film, that had not been seen since its Berlin debut. That 145-minute restored version is now available on DVD.