Paris, the Banks of the Seine? When I made a three days trip to Paris with friends we did lots of sight-seeing there, including many of the famous buildings, such as the Eiffel Tower, Notre Dame Cathedral, Sacre Coeur, Arc de Triomphe and many more, but the best thing we did there was to take a boat trip on the Seine in the evening. It's such a wonderful moment to see the Eiffe Tower by night, shining because of all the small lamps on it.
Paris in general is always worth a visit, but besides all the lovely touristy places you soon will see that those great places always are very close to poverty/poor people who suffer while tourists spend 3 Euro for a glass of coke.