Dulles Airport in Virginia is a beautiful piece of architecture by Eero Saarinen. Like most airports in recent years, it outgrew its space. In 2003, they did a renovation and expansion that I think would make Saarinen proud. It is hard to tell which part is new and which is old. They're curently doing a second expansion, I hope they hold true to the same for it as well.
I always liked the type in Dulles, even as a kid, but I could never place the typeface. It turns out that it was lettering designed by hand by Saarinen for the signage in the airport. For the 2003 renovations, type designer Christian Schwartz was commissioned to create a typeface from Saarinen's type. I noticed when I flew home for Christmas that the "jetblue" signage couldn't be original - jetblue didn't exist then. Yet, you can't tell. On Schwartz's website, he says "This face was drawn for an architecture firm working on a restoration and renovation of Dulles Airport. If I did my job well, you won't be able to tell which signs are old and which are new."
Job well done.