Yes, tonight, it is " la nuit des musées" , many museums will have free entrance and special events will be held in many places.
Personnally I think I'll be going to the Chateau d'Oiron in north Deux Sevres, where the admission is free , til 9 pm you can visit freely, then from 9 to midnight, there will be a guided visit , only lit by candlelight.. looking for ghosts maybe?
I'm sure there are events near where you are; if you are interested you should find info on the internet or in the local paper.
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