All Saints' Day in Madrid - November 1
 

Any special activities?

I assume church services, what about closures or transportation changes?

Many thanks, in advance, for sharing your experiences.

Dia de Todos los Santos is a national holiday so banks will be closed, some stores and restaurants. I just checked and the Prado museum is open! Another thing to do on that day would be to take the on/off bus tour.
I do remember reading signs posted on the bus that there will be extra buses for people planning to visit cemetaries.

Not sure about Spain... But this is my favorite day of the year in Central Europe... I always go to the cemetery in the evening.