Stop over city on the way home

A multi-city stop over city works best when it is a European hub with a nonstop back to SEA. That would be AMS or CDG, Delta/KLM?AF hubs.

PS for just connection, no stop over, yes to AMS, no to CDG.

Zurich is a good airport to connect in.

Iceland Air flies non- stop to Seattle, so Reykyavik could also work. One very full day enabled me to tour the main sights in the city, spend a long time at the Settlement Museum and also take the really informative free walking tour. The second day I went on a Golden Circle tour. The airline has "stopover" options or, just stay a couple days on your own. Caveat: it took about 45 minutes to get into the city from the airport.

Barnstormer, are you planning on flying round-trip on the same airline, or taking one over to Italy, then open to whatever airline makes your non-Italian stopover possible? On Icelandic, you pass thru Reykjavík on your way back to Seattle, no matter where you’ve departed from elsewhere. So you could definitely make stay in Reykjavík, or you could just be there for a few hours, until your flight home departs. Just in case you decided to allow a connection in Reykjavik, after doing a stay in Paris, Brussels, Geneva, or several options in Spain, Germany, Scandinavia, and the British Isles.

Similarly, Norwegian Air, who offers some incredibly low fares, but then charges separately for everything from most baggage, to meals and water on board, etc. They connect thru London’s Gatwick Airport, so London would be your direct stopover, unless you went to their cities in Spain, Greece, Croatia, or in Scandinavia, where Norwegian will pass you thru London Gatwick before flying you back to Seattle.

Perhaps Madrid or Barcelona.

In addition to Amsterdam, Paris (CDG) and Reykjavik mentioned above, you can get from Frankfurt direct to Seattle on Condor. You can also fly home to Seattle direct on Norwegian (Gatwick) and British Air (Heathrow).

A great tip I got from this forum: to see who flies where from an airport, look at that airport's Wikipedia page. Here's SEA: https://en.wikipedia.org/wiki/Seattle%E2%80%93Tacoma_International_Airport#Passenger

Note that not all flights are daily (some are as infrequent as once per week), and when a flight is "seasonal," the season can be long or short. So, you have to check available flights for your exact travel dates before getting too attached to an itinerary.

Of course, if you're willing to make another connection in North America, lots of other options open up (places like Warsaw or Vienna, that have service to other NA cities but not to Seattle). Or if you can use Vancouver's airport, you may get not only more city options, but some have reported cheaper flight prices as well: https://en.wikipedia.org/wiki/Vancouver_International_Airport#Passenger

Icelandair serves Milan but no other Italian city. Otherwise it would be Amsterdam, Frankfurt, Paris, Dublin, or London (Heathrow) -- the only European cities with nonstop flights to Seattle as far as I know.

Beginning June 1, Lufthansa also intends a direct Munich-Seattle flight pair: https://www.portseattle.org/news/port-seattle-welcomes-lufthansa-announcement-new-nonstop-service-munich.

Thanks everybody. These are good suggestions that I will look into.