What is housed inside this building in Singapore?

This airport is amazing & unique. You can spend hours wondering around & forget you have a flight to catch. It's almost a destination worth exploring. No other that I've been to compares.

I've not been to this airport😈

The Rain Vortex, sponsored as the HSBC Rain Vortex, is the world's largest and tallest indoor waterfall, standing at 40 metres (130 ft) high.[28] Recirculating rain water is pumped to the roof to free fall through a round hole at up to 37,850 liters (8,330 imp gal; 10,000 U.S. gal) per minute to a basement-level pool.[25] An acrylic funnel at the bottom prevents splashing and insulates the sound of the cascade. The toroid-shaped roof has more than 9,000 pieces of glass spanning 200 by 150 meters (660 by 490 ft)[25] with a sloped oculus as the mouth of the waterfall acting as "a continuation of the building...completed in a liquid form."[29] At night, the circular walls of the waterfall becomes a 360-degree stage for a light-and-sound show.[30]

the picture gave the answer away!!