When visiting Paris, in my opinion, it is a sin not to take in some churches, no matter your belief system they are beautiful works of art.
Notre-Dame is one of the most historic churches in the world! There is much written about Notre-Dame and I am no expert on that history. I just know what I like. I am not Catholic (I am a Christian and am a Baptist). I do believe there is only one heaven and those of us that are Christians will one day be there. Having said that I love to experience different denominations and Christian churches. I was there during the end of a mass and would recommend that you try to go during a mass, as sit for the mass as all are welcome.
I did find myself wondering what the difference between a Cathedral and a Basilica was. This is what I found out. A basilica is designated by the pope as an important church because of history, spirituality, or other significance such as architecture. Once a basilica always a basilica.
A cathedral is where the bishop’s throne is located. That throne is called a cathedra. A cathedral is a higher designation by the Catholic Church than a basilica.
Now to make matters more confusing a basilica can be a cathedral, or not. A cathedral may or may not be a basilica. For example Notre Dame is the Cathedral for the Archdiocese of Paris, it is not a basilica.