If you want to see Notre Dam, be sure to chose a time when there is lack of tourists. The ques can be awful and you be stuck for hours.
Unique Suggestions: Come back later or strategically chose another time or date.
Fun Alternatives: You don't have to get inside every history-building. Why don't buy a beer and a sandwich and have a pick-nick i the park in front of e.i. Notre Dam..
I visited Notre Dame in March of 2004 and was extremely disappointed at the changes made to accomodate tourism.
Neon signs, tents, no sign or feeling of the presence of "the Holy Spirit", more like, "the holy dollar"
Unique Suggestions: Be prepared not to be fascinated with the beauty because much of it may be scaffolded or inaccessible.
DO climb to the bell tower and share the view of Paris with the gargoyles.
The bell tower was the highlight of this visit.
Notre Dame ... an impressive Gothic exterior tarnished by the incessant haggling of junk-mongers all around it. There are infinitely better churches with some semblance of austerity all throughout Paris. I recommend visiting some of those after seeing the poor, overwhelmed Notre Dame.