As a non-Christian, how to have best Christmas Day experience in Rome?

I'll be visiting Italy during holidays and will be in Rome with my partner between 20 to 28th December. I'd have already visited monuments, Vatican City and several popular cathedrals. Being a non-Christian, I want to take care that I don't offend any locals. As most of the places will be closed on December 25th, what would be your recommendation for me to have the best experience of Rome offers with a religious perspective in mind for this day? ***Post Script**: This question was asked on StackExchange Travel community and people suggested me to ask the question on this site instead.*