Got to see one in person at an airshow with my dad back in the late 90s. It was in an random hanger we were checking out. The main door was opened maybe five feet with a gate in front of it and guards were supervising people looking in. We had no idea what to expect. I will never forget looking around the door and there it was, gave me chills. It was the coolest thing I have ever, or will ever see.
As is hackernews tradition, I will now recommend "Skunk Works" by Ben Rich, fantastic book.