Just an hours drive east of Paris through the A4 is the town Château-Thierry. It's located beautifully by the Marne river and is a historic site.
There are traces of civilization all the way back to the iron age, and a secondary Roman settlement was made on the other side of the river thriving on the river crossing. On a hill close to the river is an old fortress ruin settlement which dates all the way back to the 9th century. In the beginning of the 19th century the most of the castle was razed and now only the fortifications and a gate is left. The area is now a wonderful park with a beautiful view over the city and the nearby areas.
During the summer there's a living museum and re-enactment which shows how people lived in medieval times. It's a group called Virges Armes which is behind the re-enactment. Crafts, shows, workshops, entertainment for children, education, acting and so on.
To important battles were fought in Château-Thierry; one in 1814 during the Napoleon war and one in 1918 during the first wolrd war. There's now a big American monoment for their fallen soldiers a short distance from the town.
The well known writer Jean de La Fontaine was born in Château-Thierry 8th of July 1621. he is known for his fables about animals which were used as disguise for political messages in a time where normal citizens couldn't say their opinion about nobility too openly.
Another good reason for visiting the town is that it is located in the area that produces Champagne. It is on the "Route touristique du Champagne", which is a sightseeing route passing through the Champagne region and brings you to the best and most interesting champagne producers. Of course you can find wine cellars and tastings in the vineyards.