As far as busy international airports go, Singapore's Changi Airport is notorious for being hell on Earth — that is, if you're in a huge rush to get to your gate without being sidetracked by something that’s lush, lovely or otherwise breathtaking. Pity the traveler passing through Changi — one of the few rare airports out there where one might actually welcome a substantial delay — without more than 2 hours to kill.

It's that impressive.

After all, at what other airport will you find a single terminal that's home to a kinetic rain art installation, a sprawling cactus garden with a cocktail lounge, a rooftop swimming pool and a Burger King?

Ever set foot in an airport terminal, complete with a trio of themed gardens, that's billed as a "non-stop entertainment hub"?

Or how about a terminal that's signature feature isn't the 24-hour movie theater or massive koi pond but the world's only airport-bound butterfly garden, a lushly planted habitat that's home to more than 1,000 brightly hued resident Lepidoptera?

Obviously, a generous handful of superlatives can be applied to the three main passenger terminals (there's a fourth on the way) that compose Changi Airport, a facility that is consistently ranked as one of the finest airports in the world while also being a major Southeast Asian hub that accommodates over 55 million annual passengers.

However, it may not ultimately be the world's tallest airport slide (!) or the world's only airport nature trail (!!) that truly puts Changi Airport on the map.

Jewel Changi AIrport, Singapore Because Changi Airport isn't bonkers enough, the famously fancy aviation hub is getting a Moshe Safie-designed addition in which travelers will be "immersed in rich brand experiences" amidst a "verdant backdrop." (Rendering: Changi AIrport)

That would be the world's tallest indoor waterfall.

Due for completion in 2018, said waterfall — a 130-foot-tall cascade dubbed the Rain Vortex — will be the show-stopping centerpiece of Jewel Changi Airport, a new multi-use structure designed by lauded Israeli-Canadian architect Moshe Safie (Montreal's Habitat 67, Crystal Bridges Museum of Contemporary Art). Described as a "fusion of nature and a marketplace," the Jewel is essentially one part lush rain forest biodome and one part high-end shopping mall with a massive underground parking garage hidden underneath. Resembling a giant glass doughnut of sorts, Jewel, which also includes a 130-room hotel, will serve as a connector: It will straddle the airport's three existing terminals, allowing for passengers to move seamlessly between the structures and make them more merrily distracted/late for their flights than they already are.

But about that waterfall …

Writing for Wired, Sarah Zhang recently provided a fantastic preview of the under-construction mega-fountain. Heck, I could almost feel the spray. Or maybe that's just my AC window unit malfunctioning.

Rain Vortex, Changi Airport, Singapore Singapore's Changi Airport: One of the few airports where a 4-hour delay is a blessing in disguise. Jewel Changi Airport is a terminal-connecting glass structure that, when complete, will feature a massive indoor cataract. (Rendering: Changi AIrport)

More precisely, Zhang gets into the engineering nitty-gritty and explains how exactly Rain Vortex's creators, the Los Angeles-based water wizardry firm WET, designed a nine-story waterfall to fit inside of a structure that firm co-founder Mark Fuller describes as a "huge toroid of glass."

And because no one has ever cut a giant hole in a bagel-shaped glass roof and dropped water nine stories to the ground, the engineers on the project were concerned. 'A natural waterfall, it actually creates it own microclimate,' says Fuller. Think about it: A waterfall is water crashing through the air and dragging that air with it. It creates turbulence. It makes clouds of mist. The last thing you want is a terminal full of hot, humid air. You expect that in LaGuardia, not the world's best airport.

After a bunch of airflow studies of the glass dome, the WET team's solution was to change up the flow of the waterfall. The effects of the turbulence build up over time. By alternating lighter trickles with sheet-like cascades, the waterfall doesn't actually disrupt the air in the building all that much.

To perfect the flow, the team began by mocking up a one-fifth scale model of the waterfall. Water can be tricky to scale because it does not flow a fifth as fast in a one-fifth scale model. 'You're not scaling gravity. You're not scaling viscosity,' says Tony Freitas, the lead WET engineer on the project, ticking off the forces that affect water flow. So it actually takes extra math to convert the results from a scale model to what you would expect in the real thing. WET also built a full-sized prototype of one-third of the waterfall's edge, just to make sure water would behave as they expected. And because even that was too big to test indoors, they hoisted it up by crane at the Hansen Dam in LA, where they poured gallons and gallons over the edge of the partial model.

Yikes! All of this for a waterfall at an airport shopping mall?

Rain Vortex, Changi Airport, Singapore Rainwater reclamation will play into the design of Rain Vortex. The cascade will join existing only-at-Changi features such as a butterfly garden and a swimming pool perched atop the roof of Terminal 1. (Rendering: Changi AIrport)

It's all a bit over the top, sure, but Changi Airport is no ordinary airport, and WET is no ordinary designer of public fountains and water features.

Founded in the early 1980s by a team of erstwhile Disney Imagineers, including Fuller, Melanie Simon and Alan Robinson, some of WET's high-profile aquatic spectacles include the Fountains of Bellagio on the Las Vegas Strip, the Dubai Fountain and Aquanura at the Dutch theme park Efteling. WET has also revamped and reinvented a handful of older iconic fountains, including the Revson Fountain at Lincoln Center along with my all-time favorite water-squirting sculpture, Kazuyuki Matsushita and Hideki Shimizu's International Fountain, a landmark fountain-cum-public cooling-off place designed for the Century 21 Exposition (1961/1962) at the Seattle Center.

If you're familiar with any of the above WET installations, you're probably aware that they all have a synchronized element — basically, they're all programmed to dance. For example, the Seattle Center's International Fountain is synchronized to perform to both Beethoven's 9th and a rousing medley of Pacific Northwest rock classics, among other things. The last time I was in Vegas, I caught the fountains outside of Bellagio leaping to the sound of "My Heart Will Go On." As lukewarm as my feelings are about that painfully maudlin tune, the show itself was nothing less than mesmerizing.

Rain Vortex, Changi Airport, Singapore Flanked by shops, restaurants and an indoor forest, the mist-emitting centerpiece of the Jewel Changi Airport development will give travelers something to obsessively stare at that's not the departures screen. (Rendering: Changi AIrport)

While Rain Vortex's status as a waterfall, not a fountain system, means that it will lack the same choreography of some of WET's more dramatic installations, it will be subject to a rubberneck-inducing musical light show that will, in the words of Wired, "make the waterfall glow."

And true to Rain Vortex's name, the natural elements will play an integral part in the waterfall's groundbreaking design.

As Wired explains, the roof of Jewel Changi Airport — a "unique mixture of lush nature and urban energy" — will feature a rainwater-harvesting element, allowing the gushing indoor cascade at its center to be composed completely of recycled rainwater. WET is confident that the waterfall's rainwater-only status shouldn't be an issue considering the huge, moisture-packed tropical storms that roll through Singapore on the regular. However, if there's an extended dry spell and the rainwater captured by Safdie's structure just isn't cutting it, additional H2O can be pumped into Rain Vortex.

It's worth pointing out that exceptionally clean 'n' green Singapore is, not all that surprisingly, already home to the world's current tallest indoor waterfall, a 115-foot-tall mist-maker located within the Cloud Forest, one of two massive conservatories found at the Gardens by the Bay nature park.

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.