Some time ago I joined an international group of women who live in & around Paris & a couple of times a month we go out for a walking tour and/or a visit to a museum. It's a wonderful way to get to know other people as well as getting to know Paris better. And we preferably visit parts of the city that are a bit off the beaten path.
So last week we went to Chateau de Vincennes, at the end of metro line 1. Quite a trip from the suburbs (especially if you add some perturbation caused by a package at the Palais Royal... half an hour delay!) but absolutely worth it.