This is one of the more popular sites in Paris. It’s free. Although the line seem long at the front in the summer, it moves pretty fast. You can go by metro, bus or taxi. For us, we were on the open bus tour and just stopped on the street across it.
A lot of army people around the tourists area with really big guns which was a little off putting and scary. It doesn’t exactly scream Welcome.
Now, for the details of the church. This was on the front facade.
It’s still a working church. In fact there were masses going on. You can walk around the perimeter of the church with various displays and some exhibits. There’s also a section for souvenirs on the side. The middle area is where the mass takes place. They have flat screen TVs too around which was quite modern. A lot of people still come to pray and light their candles so be mindful of them when you come to visit. :)
They had about 3 of these for different designs. It’s like a vending machine for a Notre Dame Medallion/Coin. So have your euro coins ready. We didn’t have a lot at the time so we only manage to get one. I gave it to my cousin since I already got one in 2003 and they were the old kind where you drop a penny and a euro and twist the handle so it can turn it into a coin. :)
You have an option to climb all the way up the church but this is the line that you would have to fall in on the left side of the church.