Rouen is the capitel of the Haute-Normandie. The city is much more crowded then the others we visited. But it is also a nice city. Many old houses are still there and nice places (squares / plaza). Many of them have interesting decorated facades. You also shoud visit the palace of justice and the oldes hotel of France.
Rouen also has a famous cathedral and a memorial to Jeanne d’Arc. Both of them will have their own posts.
Although I mentioned the old houses, there are also quite modern department houses and modern shops in old buildings, the mixture isn’t bad.
Take your time for visiting this city. At least you need half a day. Better, if you can spend a whole day. When you’re in a hurry, come back an other day or come twice.