As I spend a whole lot of time in airports, I have my favorites for very different reasons. AndI am wondering what some of your favorites are and why?
I really enjoyed the Minneapolis- St Paul Airport! It is set up in a huge circle so you can walk through the whole thing. There were several legit dining options, and the convenience shops sell a lot of unique snack options, including many organic and Paleo/real food type options. I spent two hours wandering around and had lots of fun!
Usually I hate airports and try to limit the time I have to spend in them but there is one exception: Changi Airport Singapore, it is extremely user friendly with lots of good places to eat, drink, have a massage and, if you have a long layover there is a hotel with an outdoor pool on site where you can spend a few hours. In Europe there are three that are bearable: Carcassonne Airport Brindisi and Bergamo mainly because they are easy to get through!
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I am shocked that no one has mentioned the Portland International Airport (PDX)! It's beautiful inside with incredible restaurants, great shopping, unique art pieces sprinkled throughout the airport, coffee shops, wine bars and phenomenal beer, and often live music. I have family there, so I'm always a bit sad that I don't have a layover because it's just a great place to be.
I haven't had very long layovers in many places but I love food and drinks so Denver International Airport is a great place to spend any length of layover. It has some the the best beer, food, coffee I have had, especially in an airport!