Paris, three wonderful days:
You can pick up a bike at any Vélib' station and return it at any other. Just to make sure you that don't keep it, you'll be required to supply credit-card information before taking a bike, and the bike will sound an alarm if you try to haul it back to Huddersfield or Hackensack.
American credit cards don't work in the vending machine, but if you try the other payment option: You can buy a 1- or 7-day Vélib' ticket on the Web.
Vélib' bikes are popular, and occasionally you'll find that all bicycles are rented. Less commonly, you may go to return a bike and find that all the available slots are occupied. (If this happens, try another station; they're scattered across the city and are usually no more than 300 meters apart.)
If you are planning a visit in the Marais, in Paris; they are all great but stay away from the very famous Les Marronniers or just experience the worst service ever in your life; if you are lucky, you will be yealled at because the poor waitress is tired and that the fridge does not work, and it is your fault !! Rather, try Cafe Vitto, on the right of the previous one, they are charming, good service, and prices are so much better anyway !
You can easily find a three course meals for 10 euros at lunch time and 18 euros at dinner time; dont hesitate to have the pitcher of wine for the beverages: Rosé is for sure the best if chilled and if you go at summer time.