A word of advice...take a Seine river cruise when you are in Paris. I mean it. Some people disparage this activity as "tourist-y" and I am here to tell you - No way!
It is a lovely way to spend an hour relaxing and soaking up the sights. You can see a string of landmarks from a great vantage point (Notre Dame, the Louvre, Musee D'Orsay & the Eiffel Tower to name a few) all while planning your next adventure. (For example, we decided that after the "cruise," we should head over to Ile Saint Louis for some ice cream.)
When you board the boat, I recommend choosing a seat on the railing, so that other passengers won't accidentally block your photos. This shot shows a glimpse of Notre Dame and what I really like about it is the people relaxing on the steps that lead down to the river.
When our boat passed by these steps, look at the reaction of the man & woman. Pure joy. That is what visiting Paris is all about.