Pan Am's Dinner Key terminal on Biscayne Bay for the flying boats. It's still there, hangars and all. But, the terminal itself is now the Miami City Hall, recently partially restored to her glory gays.
Pan Am often built their own airports in the beginning.
The skylit end of the D terminal at PDX was originally designed for Delta and their hub to Asia. Portland eventually used the design for the rest of the Airport in the remodel the past years, thus PDX has become an "H" design as opposed to the old "Y" design. The old Delta skylights now span the whole D and C terminal. It's becoming a beautiful airport, although it's too bad we don't see too many heavies.