Much has been written about “the other Paris” (or, to be realistic, “the other Parises”), but Julian Green (sometimes written as Julien Green) sums it up nicely:
Paris is a city that might well be spoken of in the plural, as the Greeks used to speak of Athens, for there are many Parises, and the tourists’ Paris is only superficially related to the Paris of the Parisians. The foreigner driving through Paris from one museum to another is quite oblivious to the presence of a world he brushes past without seeing. Until you have wasted time in a city, you cannot pretend to know it well. The soul of a big city is not to be grasped so easily; in order to make contact with it, you have to have been bored, you have to have suffered a bit in those places that contain it. Anyone can get hold of a guide and tick off all the monuments, but within the very confines of of Paris there is another city as difficult to access as Timbuktu once was.
From Paris, by Julian Green (published 1991).