Strasbourg's historical center is located on a big island, where you could find the famous Gothic-styled Cathedral and the beautiful area of "Little France" with the typical wooden houses. Strasbourg is also famous for its X'mas market.
Either wandering in the city discovering each little corners, or climbing up the Cathedral, or taking the boat tour along the canal with a vivid explanation of the city stories would be very nice. More over, the boat tour will take you to a new area of the city where the European Parlement is situated.
Don't miss out the delicious food in Strasbourg. Choucroute(different kinds of pork and sausages), Tarte Flambée, Baeckoff, Brezel bread, varies beer and wine. However, the Salad Alsacian really surprised me, as I was expecting something "green", I've got a big portion of cheese with sausages on the top and it was tasty!
For some historical and geographical reasons, Strasbourg has mixed culture of France and Germany, through the food, the language, way of living, etc. It recalls me "La dernière Classe" of Alphonse Daudet, which I learnt in the primary school.
Alphonse Daudet : La dernière Classe
Around Strasbourg, Colmar, a picturesque town lies in the south part of Strasbourg. Only 30 mins by train to get there from Strasbourg station. If you have even more time, you may also cross the frontier to enjoy the thermal in Baden-Baden, Germany.