Among the Paris locations found by Albert Capellani in 1913 for his historical drama Le Chevalier de Maison Rouge was the cour de Rohan, also known as the cour de Rouen. This is a set of courtyards with parts dating back to the thirteenth century, though most is from the sixteenth century onwards, such as this well:
But the most often represented feature of the cour is the staircase:
Here it is in a postcard, franked in 1908, and in a photograph by Atget from 1915:
It was photographed by Marcel Bovis in 1938 and by Janine Niepce in 1957:
And Mark Shaw photographed a Chanel dress there in 1955:
Just up those stairs was the painter Balthus's studio. When Leslie Caron runs up them, as Gigi, she appears to be going to visit him:
When Louis Jourdan comes down into the courtyard after visiting Gigi, in the next shot he is in the rue de Furstemberg, which is where Balthus had a studio before coming to the cour de Rohan. These are strange coincidences.
L'Escalographe is an occasional blog about stairways in Paris that appear in films
My chief work of reference is François L'Henaff's magisterial Paris en marches: les escaliers des rues de Paris, published by the APUR, and available here.