Regarding Paris Churches I agree with Sainte Chapelle ... The first time I went I was wondering what all the fuss was about...in the basement level... until I found the stairs up to the main attraction.
Sacre-Coeur, Montmartre I loved too. I was so lucky to be there on a day where the masonry was being cleaned. I have some great side by side pictures of the dirty grimy masonry next to the just cleaned masonry. Night and day difference. This was about 5 years ago so I assume it still glows.