Paris is pretty sweet - just, for the love of God, don't fucking drive. The metro and easy access to long distance trains make it a pretty frequent stop for me.
Driving in Paris is crazy as hell, and I did drive a lot in European cities. Although the worst I've ever been to has to be Bucharest. People drive hyper-crazy in Romania.
Stay overnight next time! The town surrounding the citadel is actually really pleasant and one of the staples of cuisine local to that area is Cassoulet!