The Bois de Boulogne was and still is a very nice place in the daytime, and I would say fairly posh to have a flat/house around there. At night however, it has become (in parts of it anyway) a meeting place for prostitutes, transvesties (not sure of spelling), and couples looking for other couples - if you know what I mean!
On the other hand Sarko used to do his jogging in the Bois every morning - together with bodyguards of course!