Conversation so far:
what year was Gigi released?
In March 1957, the duo began working in Paris.
who developed the main character?
so Lerner agreed to write the screenplay only.
He and Freed discussed casting.
how did they pick the cast?
He and Freed discussed casting; Lerner favored Audrey Hepburn, who had starred in the Broadway production written by Loos.

Question: how did they choose the location?
Self-contained rewrite: How did Lerner and Freed choose the location for the film Gigi?