The Boeing Assembly Plant and Future of Flight Aviation Centre is located 25 miles (about 40kms) north of Seattle, and of course, I went along.
Unfortunately you cannot take photos in the factory itself but you can see some here on their website – it is mind-blowing how enormous this place is. From the tour balconies you can see airplanes under the various stages of construction, from the individual components until they are all assembled as one.
I tend to under-appreciate aircraft in general, but this experience really gave me a whole new level of understanding. The number of people, parts, assembly space, safety checks and general logistics that goes into a massive project like this is incredible.