With the MOA rally in Redmond Oregon next July, I thought I'd offer some suggestions about unique places to experience. I'm sure that others in the area will add to this.
First, be aware that the largest building in the world is located at Paine Field just south of Everett, WA. It's the Boeing final assembly plant for the big planes such as 747, 767, and 787. I was riding by the building once on highway 526 and I clocked something like 13 seconds at 55 mph, to get from one end of the building to the other. Not too long after that, they expanded it and made it even bigger.
Boeing has an information center called "The Future of Flight", and also a factory tour that takes you right into the final assembly building and up to a balcony where you can look down on several huge planes being completed. Tours are hourly from 8:30a to 5:30p daily (except holidays) The info center includes stores where you can purchse Boeing memorabilia (want a leather flight jacket?) and a cafeteria. Be aware that you can't bring backpacks, cameras, cell phones, binoculars, etc.
For information, seasonal pricing, and advance ticket purchases, go to www.futureofflight.org or telephone 800 464-1476. Yes, get tickets in advance if you want to go; this is VERY popular.
Visitor center location: 8415 Paine Field Blvd. Mukilteo WA (about 30 mi N of Seattle, via I-5 and west on 526.