The Musée d'Orsay has more famous and familiar paintings per square foot than any other museum I've ever visited. It's an astounding collection for any museum, let alone a museum that opened in 1986!
Regardless of what your Paris guidebooks may tell you, if you want to visit the street markets of Paris, you better go first thing in the morning and preferably on a weekend.
I've now seen three Statues of Liberty (NYC, Tokyo, Paris)
Hot dogs are much more readily available in Paris than I ever would have imagined.
One of the few American meals that I miss while traveling is a nice greasy breakfast. Fortunately, we were able to get one in Paris.
When visiting places with a lot of history, it's interesting to see what events and people they choose to focus on at their historic attractions. Most of the historic attractions in Paris focused on the revolution, of course. In Vienna, they seemed to focus on Maria Theresa and Franz Josef I, their most famous and last* monarchs, respectively. Marie Antoinette comes up quite a bit in both cities, since she was the daughter of Maria Theresa and wife of Louis XVI.
* Technically, Franz Josef I wasn't the last Habsburg monarch, but he reigned for 68 years and the monarchy was dissolved two years after his death
I've developed a fondness for Roman Ruins, no matter how unimpressive they are.
French coffee is stronger (and better) than Viennese coffee (Don't take my word for it, however, as I only had coffee one time in each city).