Conversation so far:
What year was the film, Gigi released?
The film, Gigi released on May 15, 1958.
Who developed the main character for the film, Gigi?
The screenplay of the film, Gigi by Alan Jay Lerner is based on the 1944 novella of the same name by Colette.
How did Alan Jay and Arthur Freed pick the cast for Gigi?
Alan Jay Lerner and Arthur Freed discussed casting; Lerner favored Audrey Hepburn, but Freed preferred Leslie Caron.
How did Alan Jay Lerner and Arthur Freed choose the location?
In late April, Freed and Minnelli and their respective entourages arrived in Paris. The weather had become unseasonably hot, and working in hotel rooms without air-conditioning was uncomfortable.
How did Arthur Freed and Alan Jay Lerner come up with the score development for the film, Gigi?
Lerner approached Loewe, and when he suggested they compose the score in Paris, Loewe agreed.

Question: where did they film most of the movie?
Self-contained rewrite: Where did Alan Jay Lerner and Arthur Freed film most of the movie Gigi?