Where to go?

You could head down to the French coast along into Italy. Very easy to get to by train and there are some great towns along the coast line.

Venice!

Just, got back from 21 days 6 countries, #1 was Lauterbrunnen Valley Switzerland, #2 Paris #3 Cinque Terre, Italy

Brussels! Sometimes it gets a short shirf, but I loved it and want to return. Lots of very interesting sights. I took a walking tour. It is easy to get around. Great food, excellent chocolates, and friendly people. Battle of the Bulge was nearby. Both Bruges and Antwerp are a worthy stops.

I have been to Venice twice. It is decaying and a shell of its once glory. The floor of St. Mark's is sinking up to one foot in some places!

If I had three weeks, I would create a loop (start and stop in a different place) and rent a car. For example, spend 3-4 days in London. Take a local train to Dover and a hydrofoil across the Channel. Or take a train from London thru the Chummel to Pairs. See Paris & then pick up a car. Used Andy Bestow's car rental serivce. Create a loop thru Belgium, Holland, & Luxembourg. End at the Charle De Gaulle airport. Drop the car. This is an "Open Jaws" ticket. I have used a Eurail pass, but I prefer a car because it is more flexible.

A

Hello, Heidi!
After large cities, we suggest a change of pace -namely a small, wonderful, Austrian alps, 4,000 year old village: Hallstatt. It's gorgeous. So are the villagers.
You may get there by train. A passenger launch meets every train to take you across the lake to Hallstatt. To check it out, go to www.Google.com, click on "Web" - then type in "Hallstatt, Austria". You will have several good web sites to review.
Whatever you do, have a great trip... P.

Why would you choose anywhere else, you already have three major countries to see. London is worth at least 4 or 5 days, PLUS do a few day trips, Bath is excellant, and for the teens Warwick Castle( google it) is definately worth a day also. There is also Brighton if weather is nice, walk along board walk etc. I like Hampton Court also.
Then Amsterdam, well, that is worth 4 days, so perhaps you could then travel to Paris via Brussels, which would give you the extra destination you think you need, and yet you would not be going out of your way. I am not big on Brussels, having just passed through it, so to me I figure it is only worth a day or two,, but I am sure others who liked it could give better advice.
Paris is easyily worth ten days,, 5 or 6 in the city, and then there some incredible day trips to choose from, Versailles, Chartes, Loire Valley Chateaus, Chantilly( do your kids like horses) , D Day beaches( this is actually worth two or three days) etc etc.

Did you buy a Eurail pass? In that case definately do Mont St Michel and D Day beaches,,

Heidi, I would try to stay in that corner of Europe to maximize your sightseeing time and minimize your "en route" time. Also, do something different than the large cities as you will be seeing 3 of them already. The Rhine and Mosel valleys would be a great change of pace between Amsterdam and Paris.

Check out Rick Steves' Germany, Austria and Switzerland book for more information about the Rhine and Mosel. Make sure to see Burg Eltz. Enjoy!

Thanks to everyone who responded. It's great to have the advice of seasoned travelers.

All of the places suggested by other persons here are good places, but I agree with Pat in Victoria : if you go to those three countries, stay in those three countries.
England and France have enough good places to keep a tourist busy for several weeks. In England I think York is better than Bath. (Both of those towns have a medieval center). In my opinion, going to Amsterdam is not a high priority, but I suppose you want to go to somewhere in the Netherlands to meet some of the delightful people there.

I would suggest Austria (the Salzburg area) or Scotland. Both are "do-able" We took our son and daughter to both places when they were teens and they loved both.