While waiting for your flight, you can take this unique opportunity and visit a butterfly garden that is a part of the airport complex. More than 1000 butterflies of 40 different species to be seen. There is also a grotto waterfall in the garden.
The garden is situated in Terminal 3, Levels 2 and 3.
Official website http://www.changiairport.com/en/airport-experience/attractions-and-services/butterfly-garden.html
Address (Unnamed Road), Changi 81, Singapore
Coordinates 1°21'27.144" N 103°59'10.245" E