Sadly, I believe this is the terminal you are thinking of -- once upon a time ago, it was the Pan Am WorldPort.
Pan Am built the terminal in 1960 as a showcase for international jet travel and is known for it's "Flying Saucer" roof.
More info:
http://en.wikipedia.org/wiki/Worldport_%28Pan_Am%29
It is a piece of history, but sadly Terminal 3, which was once the Pan Am WorldPort will be destroyed. T3 is still in use by Delta Air Lines, is in need of upgrades, and just can't handle the passenger traffic.
It was operated by Pan Am until 1991 when they declared bankruptcy, at which point Delta Air Lines purchased the building.
Using the T3 US Customs & Immigrations facilities is like taking a step back in time.
Here's a pic of the terminal that I took:
Now, there is the old TWA terminal as well. This is being preserved and is also a piece of history.
This terminal has been designated an NYC Landmark and is being renovated so that it can be opened to the public again.
It was built around 1963 and was known as the Trans World Flight Center. From what I understand, it was always a TWA facility until TWA shutdown.
Here's a pic of the TWA Flight Center that I took from the JFK AirTrain
For those wanting to photograph history, from public airport property, I should note security guards and JFK AirTrain employees will harass you for taking pictures from the JFK AirTrain. Apparently taking a photo of this magnificent building
IS a suspicious activity.
SDF_Traveler