Originally Posted by
aa4ever
I agree that Bruxelles isn't undoable, but I would be hesitant on Bruges. That would require roughly 2.5 hours each way of transit (assuming little-no layover), which is 5 hours transit in one day. I also wasn't wowed by Bruges, but I know a lot of people (especially a lot of people I know in France) really like it. I personally prefer Brussels, which I found to be an enjoyable city.
The suggestion of Rouen is also a good one I think, as it's under 1.5 hours from Paris. One other suggestion could be Mont St Michel if OP would like to see it (doable either by driving or by TGV to Rennes and then a bus from there).
My personal choice would be to book all 10 nights in Paris and then, if bored, do a day trip or two.
A single day in Brussels? Yeah, did that, and what you come away most with is a wish that you had another day. I'd want to spend two days there; lots to see by foot the first day, just walking around, then on the second day you could make use of their public transit and see things a bit further out.
Paris is a tough one. It's not as if you can get much of a taste of Paris in just a few days. I think it's better suited for 3 or 4-day trips with frequent returns. Each trip plan on 2 or 3 really significant outings in different areas. Don't forget to see a flea market at some point! And when you hit the Louvre, either have a very strict time limit or plan on spending way more time there than you have time for. One or the other. It's going to wreck everything else planned that day if you let it. Or just plan the spend an entire day there if you want. Just don't think it will be easy to get away. If pressed for time, skip it entirely and see the Musee d'Orsay.
Mont St Michel is a long one-day trip. It's a must-see at some point, but in March it's going to be pretty cold and probably very wet.