Largest building (by volume) in the United States
There are hourly tours of the Boeing factory floor in Everett, but they are politely insistent that you bring no cameras, celphones, videocams, or any other recording equipment inside. (They also forbid skirts and kilts, which is somewhat more explicable given that much of the tour consists of walking around on a catwalk above the work floor.)
Sometimes they leave the doors open so you can see inside. But not the day I happened to visit.
So you’ll have to settle for this shot of one of the hangar doors, which I got by driving as slowly as practicable in the fast lane of the highway that goes right past the doors, four or five times, and pointing the camera in mostly the wrong direction. To the driver of the black VW beetle with the “For Sale” sign soap-painted in the window: I apologize, it won’t happen again.