Montparnasse became famous at the beginning of the 20th century, when it was the
heart of intellectual and artistic life in Paris. From 1910 to the start of World War II,
Paris' artistic circles migrated to Montparnasse. Later intelectuals and artists from
all over the world came to Montparnasse. While the area attracted people who came
to live and work in the creative, bohemian environment, it also became home for
political exiles such as Vladimir Lenin and Leon Trotsky.

For more information see http://en.wikipedia.org/wiki/Montparnasse.