We found out about this museum recently from this article on Petrolicious.
On the Route Napoleon in the picturesque village of Castellane. The owner has been collecting pre-war Citroens for 34 years and will only accept ‘untouched’ models to his collection.
It must be worth a stop off. We wish we’d know about it before our last trip to Monaco and will certainly add it to our list for our next visit.
Check their website or call for opening hours.