What are worthwhile excursions depend on your tastes of course. However, Paris is a wonderful city and you can't begin to experience it all in one week so I'd recommend spending as much time as possible exploring the city. Visit the neighborhoods, wander the streets, stroll the street markets, stop to listen to the street musicians, take long casual lunches. Paris is best enjoyed at a leisurely pace. The guided tour of the city and the Seine cruise are worthwhile if you haven't seen the city before. If you want to see ridiculous opulence visit Versailles. Bob, Philly, PA - Paris extension to QM2 Crossing 2006 and City Stay 2009.