Amsterdam's Schiphol airport is the single greatest airport I've ever been too. It's big, nice, fun and it works. There is stuff to do. There is an observation deck. There is even a museum (I didn't make it there though). Lot's of good food options, including an in airport grocery store.

There was also a weird blue-man-group-style message crawl in one stairwell with strange quasi political (and English language) messages. They made me laugh. The only one I can sort of remember was something like "Self confidence is ignorance".