Answer:
In Paris but not in France the thinnest of its siblings.
What has many keys but can't open a single lock?
Without a bridle, or a saddle, across a thing I ride a-straddle. And those I ride, by help of me, though almost blind, are made to see. What am I?
I have a strong affection for belly buttons.
What building has the most stories?
No matter how little or how much you use me, you change me every month.