I just realized when proboards was going crazy last Thurs my post didn't go through...
I've only been to three of the locations but, here's my preferences:
- London: Borough Market (open Thurs-Sun) and follow Rick Steve's Westminster walk
- Paris: Fat Tire Bike Tour (it's a few hours and gives you an overview of the city as well as history) and picnic in the field at Eiffel Tower, go up tour (if you can get reservations, if not then I'd go up Montparnesse at night if you can).
Food: Lunch at Printemps roof-top cafe. Cheap, decent food and awesome views.
- Amsterdam: Anne Frank Haus; hands down. Must go even if you wait in line. I doubt Kuekenhoff Flower gardens are still in bloom, but if they are, I would go.