Have to see sights in Paris?

I have heard from friends that have gone to Paris that the Louvre and Notre Dame are must-sees during the day, and that the Eiffel Tower is absolutely breathtaking at night. Although I have never been to Paris, I have heard good things about Monograms. Their website has a list of must-see sites in Paris that highlights some of the hidden-gems of the city. Check it out: http://www.monogramstravel.com/local-host-picks/paris/.