We planned to go to Versailles .. Learned it is closed on May 1 as are all museums?!
Yes...May 1 is Labor Day in Europe. Next week is another major holiday. V-E day is celebrated May 8, and May 9 in other parts of Europe.
A lot of places will be closed but lots of activities on the streets! It's a fun day.
I was in Paris on May 1 a few years ago. All museums and shops are closed. The Eiffel Tower is open (and the queues very long). Notre Dame and all other churches are open, but in the case of Notre Dame there was a long queue to go thruogh a security check.