Singapore’s Changi Airport has a two-story butterfly garden with a 27-foot waterfall, a garden with around 40 species of cacti, and orchid and sunflower gardens. It also hosts a rooftop pool, several in-terminal hotels, one of the world's tallest airport slides at 4 stories high, and a Fish Spa that offers treatments like hot stone massages, fish pedicures, and ear candling. There's a reason it's regularly ranked the No. 1 airport in the world.