Where's good to visit on a day trip from Paris, ideally somewhere you can stay overnight? Am going for five days in a few weeks and that feels a bit long to spend in one place so would like to get out of the city and explore a bit.

Already read this very helpful thread http://drownedinsound.com/community/boards/social/4255235 so don't need suggestions for stuff in Paris. Only OUTSIDE. And not EuroDisney. Mercy Bookoo.