I was very close to skipping The Louvre on the basis that it's just the biggest tourist hole in the world. Thankfully I did not do this.
I could have walked The Louvre for days on end (and not just because it's so damn huge).
I spent about 3 seconds seeing the Mona Lisa and 6 more hours walking the parts of the museum that were not crowded. It was wonderful and I look forward to returning.
