The waterfall lives inside a glass dome called Jewel. From outside, Jewel looks like a giant donut-shaped greenhouse. Inside, water tips through a hole in the roof and falls 40 metres - about as far as a 13-storey building - before disappearing into the floor.
On rainy days, the waterfall uses real rainwater. Pipes catch the rain from the roof and channel it down into the vortex. When it isn't raining, water from a giant tank takes over. The whole thing is pumped back up and round again - the same water can fall over and over.
Around the waterfall, a small forest grows on terraces. More than 2,000 real trees and 100,000 plants live there. Visitors can walk through it, ride glass-bottom skywalks above it, and watch the planes outside through the curving glass.
Changi is famous for being one of the friendliest airports in the world. It also has free cinemas, sleeping pods, a butterfly garden, and slides you can ride between floors. The waterfall is just the centrepiece. The idea is simple: travelling shouldn't be boring.