3 day stop en route to Moscow - where would you go?

I recommend Paris based on your preferences especially if you have never been there. I was there for the 3rd time last September and never tired of it. I am sure many will agree! Wherever you decide will be awesome. It is Europe after all!!

We have lived in London, Paris and Prague and I would recommend Prague for the live music, architecture (the city is like an art museum), markets, museums, great good, and its unique look and history. On the other hand, why not try St. Petersburg, Russia since you already have permission to enter the country? It is a gorgeous city and the Hermitage is even better than the Louvre (I love both). This is an easy transfer to Moscow for sure.

Out of your 5 cities there are direct flights from Seattle to London and Paris. You already have been to London. Your choice is easy - Paris. My educated guess is that there is a direct flight from Paris to Moscow.

Direct Flight Seattle Stockholm 1 day, take night ferry to Helsinki 1 day, take train to St Petersburg 1 day...fly, bus or train to Moscow.

If you've never been, you should go to Paris!

I've been to the places you listed, and while I'm glad to have seen all of them, I regret not going to Prague sooner. In my many years of travel, it exceeded my expectations - along with the other places in Czech Republic. I think our River Cruise from Moscow to St. Petersburg had a flight via either Copenhagen or Stockholm, both of which would be great visits.

Be aware of European vacations in August.

Kathleen has really good idea. Unfortunately there is no direct flight to Stockholm from Seattle. But you can do it with one change. That ferry from Stockholm to Helsinki is exciting. Then train from Helsinki to St. Petersburg. I would not recommend bus from S.P. to Moscow. It takes too long. Take fast train Sapsan (about 4 hours). It is expensive but worth it. Other trains take 8 to 10 hours. In that case take overnight sleeping compartment but it is not much cheaper than Sapsan. This could be your alternative to Paris.

In July, my first choice would be Stockholm. The Swedish summer is just beautiful. There is lots to do in Stockholm. The Vasa Museum is one of a kind. The Stadshuset (where the Nobel Prize is awarded) has a great tour. Good food markets are at Hötorget's Saluhallen (modern, ethnic, less expensive) and Östermalms Saluhallen (traditional, more expensive, and beautiful). There are a number of music venues. The only downside is that beer is expensive. If you take the ferry to Helsinki, you will find cheap beer on the ferry.

You could fly to Stockholm and then fly to Moscow
OR
overnight ferry from Stockholm to Helsinki. Spend the day there (leave luggage at locker in train station before Taking the overnight Ferry (St Peter Line) to St Petersburg. The St Peter Line goes every other day). Spend a couple of nights there before taking the train to Moscow.

Last summer, I traveled Helsinki - St Petersburg - Helsinki - Stockholm using the ferries, so feel free to PM me if you have questions. I also lived in Stockholm for a couple of years, so am a bit biased :)

Thanks for the feedback, everyone! For the record, while I would love to visit St. Petersburg (I feel like a bad Russian person having never been there), I don't think it's the right fit for this particular trip, since the whole idea is to take advantage of there being no direct flights to Russia and making an extended layover somewhere in Europe.

I have to say, I'm a little surprised at the recommendations for Stockholm/Helsinki/St. Petersburg itinerary, given this forum's propensity to advise against such fast-paced trips! It actually sounds amazing, but I think I'd prefer to stretch that trip into at least a couple of days in each place :)

I am definitely being swayed in the direction of Paris at the moment! Neither of us ever had a strong interest in specifically visiting Paris, but with direct flights to/from Moscow, this seems like the perfect opportunity to check it out and maybe fall in love with it the way everyone else seems to be! Although I am still kind of attached to the idea of checking out Dublin or having the excuse to drag my husband back to London so soon after our last trip.