I just saw a short report on http://www.bild.de (sorry, in German only) about attractions at airports.
https://www.bild.de/reise/fluege/fluege ... .bild.html
Two really nice ones are mentioned but there are probably many mores:
- Swimming pool at PUJ (Punta Cana):

https://bilder.bild.de/fotos-skaliert/g ... 0.bild.jpg

https://bilder.bild.de/fotos-skaliert/g ... 0.bild.jpg
- Beer brewery at MUC:

https://bilder.bild.de/fotos-skaliert/d ... 0.bild.jpg