What to combine w/ Paris for 3 nights?

How soon are you going? London is fast and easy on the Eurostar, but the prices get ridiculously expensive as your dates near.

The Loire Valley has a special place in our hearts. Frequent TGV service between Paris and Tours (St Pierre des Corps). From there it's easy to rent a car for a few days to tootle around to the various Chateaux, or vinyards. We love staying in or near Amboise. One of our favorite hotels is Chateau de Pray, just outside the town, with a very good Michelin star restaurant.

Depending on when you go, you can definitely do London via the Eurostar though it would probably be more like two nights since I would advise to return to Paris the night before you train leaves. If your looking for more a big city feel Brussels is a two hour train ride away and has enough to keep you occupied for a few days.

You could also visit Chartes for two nights as it's an easy train ride from Paris. Apart from the cathedral, they have an art and agriculture museums and some of the best crepes I've tasted.

I loved Colmar. I would love to go back to Alsace someday - and back to Normandy, too!

How about Belgium? Unless you really want those five nights back in Paris. Just three nights up there might be too quick - but if so, I'd probably depart by train directly from CDG to Brussels (and then may be Bruges or Ghent) and come back to Paris for the end.

If you don't mind another city, albeit one that's completely different in feel from Paris, look into Lyon. By TGV, it's only 2 hours from Paris. RIck's France book has a very good chapter on the city.

I also loved Bayeux and can understand your desire to return there.
It is easy to take a high speed train to Strasbourg, a very pretty city near the Alsacian wine villages. We stayed there several nights and then moved to Riquewehr for another three nights or so. Thatched roofs, flower boxes, charming.
Another easy choice is to take a train to Dijon or Beaune in Burgundy. We have spent quite a bit of time there. Three days would be perfect for Beaune.
Or visit Reims and The Champagne houses there and in Epernay.

All good ideas, I think, except London. Even though the Eurostar is fast and convenient, and cheap enough if you book way ahead, you won't have enough time there to really appreciate that great city. After all, you've already had five nights in Paris and you're planning five more. Most would agree that London deserves about the same amount of time as Paris, so I'd suggest a separate trip there if at all possible. Plus, as you say, it's another very big city, and you may be looking for a smaller-city or even rural experience. Stick with France for this trip, you have lots of good choices.

Thank you for all of the advice! I should have included in my original post: we aren't going until mid-March, so we have plenty of time. I know we are taking a bit of a gamble in terms of weather, not sure if that changes any of the recommendations.

We also spent some time in Bruges and Brussels last summer, and while we loved Bruges we probably will go somewhere different this time.

My wife and I went to Paris last summer. We started the trip in Paris and ended in Barcelona - with stops in Dijon and Lyon along the way. We loved Dijon - and from Dijon you can take a day trip to Beaune (which is beautiful). I think 3 days there would be wonderful and a bit relaxing coming from the big city. We had the perfect hotel in Dijon - if you're interested in more details - just let me know. But whatever you decide - have a wonderful trip!!!

All of your choices are feasible. In March I would not want to go too rural, and your time frame argues against a car (too slow compared to TGV).

Given all that, I'd go with Lyon. it is a great destination and the logistics are very sweet with Paris. (If your return flight is not too early, you can even take the train from Lyon to Charles deGaulle, direct, no stops in Paris, 2 hours.)

That said, if another place just calls to you, go there.

Dijon/Beaune seems lovely. Also still drawn to Colmar. Decisions, decisions...

If it helps, the ideal situation would be somewhere we can get to easily from CDG on our arrival day, rather than having to go into the city and transfer. That way, we could begin our trip somewhere and then come back to Paris to finish our time and easily get to the airport.

On what site and airline did you get that fare???
Lucky!

IcelandAir, direct from their website! We did book the cheapest economy fare, but we've only travelled with a carry on for a few years now so it should be just fine for us.

I’m not sure what it’s like in March but another option would be Reims. Easy 45 minutes or so ride from Paris Gare de L’est. Visit some champagne cellars, Reims Cathedral, museum of the surrender (WW II). Plenty of restaurants and cafes.

Rouen is quite a nice little city and only about an hour by train from Paris.
You might go there first, dealing with jet lag in a smaller and more pedestrian friendly place.
Then you could spend your full 5 nights in Paris and only have to change hotels once.