At 830 m from base to tip, Dubai’s Burj Khalifa is the world’s tallest building—for now.
Iwan Baan
July 9, 2015 12:16 PM EDT

If you take the world’s longest elevator ride up the world’s tallest building and venture out on the world’s highest outdoor observation deck, the sensation is a bit like being on an airplane that is idling midair to allow passengers to peer down at the earth. The term bird’s-eye view hardly describes it, since the 124th floor of the Burj Khalifa in Dubai—452 m above the ground—is higher than the cruising altitude of many birds. Walking out on to the deck, Adrian Smith, the architect who designed the Burj, stands stunned at the crowds of tourists snapping photographs of the view. “Wow, it is great to see all these people here,” says Smith, who is back at the Burj for the first time since it opened in 2010. “This place is busy.”

Five years after it debuted with Dubai-style gaudiness, including a giant fireworks display, the Burj has become a magnet for the roughly 1.5 million people a year who shell out $54 for tickets to the observation deck, perhaps to contemplate how this gravity-defying building stays upright. From its base to the tip of its spire, the Burj is 830 m—almost double the height of the Empire State Building.

And yet the Burj will likely hold on to its title for only a few more years at most. The scramble to build higher has accelerated so fast in recent years that skyscrapers that awed us last century barely warrant a mention today. Just 15 years ago, buildings higher than 200 m were extraordinary, and there were only 263 of them in the world. By 2012 there were nearly triple that number. Currently, there are about 10 buildings under way that will be higher than 500 m, which is higher than the world’s tallest building in 2003, Kuala Lumpur’s Petronas Twin Towers. More than the expression of intricate engineering, the supertall towers have become an outsized shortcut to global importance. “If you want to be a serious city, you have to show you are serious,” says Alejandro Stochetti, a director of Smith’s company, Adrian Smith + Gordon Gill Architecture. “For that, you need an iconic building.”

And if you want that iconic, sky-­scraping skyscraper, Adrian Smith is your man. Smith is among a small club of architects who design record-tall buildings­—though you wouldn’t know if from meeting the 70-year-old. About the only thing that marks the soft-­spoken Midwesterner as a “starchitect” is his trademark all-black outfit. Smith offers no gushing commentary about his buildings, preferring the results to speak for themselves. He says he has held a passion for tall buildings since at least the age of 13, when he began sketching 40-story towers—­buildings that would have been hugely tall in the 1950s. “No kids drew that,” he says, laughing.

More than a half-century on, Smith is nowhere near done. He spent decades at Skidmore, Owings & Merrill (SOM) in Chicago, where he began by working on the 459-m (base to tip) Hancock Tower before leaving to start his own firm in that city in 2006. The timing was good: Burj Khalifa, which he designed while at SOM, was being built, and oil-rich countries like the United Arab Emirates had plenty of money to spend. Smith hooked clients in China and the Persian Gulf who were eager to have him try to break his record.

When Smith met TIME in Dubai one evening in June, he had just come from signing a deal across town to design what will be world’s tallest office building (the Burj’s 163 floors have apartments and the Armani Hotel), which will anchor a new mega-development near Dubai’s boat marina, timed to open when the World Expo is held here in 2020. Though the new building’s height is a secret, he says the Burj will remain taller. Yet Smith will design offices all the way up, rather than pad out its final height—as the Burj and many others do—with a needle-like spire and top floors too narrow for use.

Then there is Smith’s most extreme project yet: Kingdom Tower in Jidda, Saudi Arabia. When it opens in 2019, it will be the first building ever to exceed 1 km. Its vast interior will have 59 elevators­—five of them double-deck so they can stop at two floors at once—that will travel at speeds designed to prevent ears popping. Financed by the Saudi billionaire Prince Alwaleed bin Talal, the tower will anchor a new suburb of Jidda, called Kingdom City, which the Saudis hope will draw millions of pilgrims traveling to nearby Mecca and Medina.

Although Smith says there were few dramatically new technical challenges involved in reaching this height, supertall buildings do not come cheap: the Burj’s final cost was about $1.5 billion. Construction can also drag on for years. Kingdom Tower’s workers spent more than a year simply digging a foundation strong enough to support its structure, which will have 157 occupiable floors and use about 80,000 tons of steel. “These buildings are massive efforts,” Smith says.

Still, the drive to build upward continues, in part because supertall buildings can transform an entire city. The Burj stands in what was a decade ago a quiet area on the wrong side of town. Now it anchors what’s known as Downtown Dubai, with a massive shopping mall, five-star hotels and office towers. Tom Cruise even scampered up its side in the film Mission: Impossible—Ghost Protocol. But such supertall buildings rarely pay off financially; the Burj itself has had trouble filling up. “There are a number of reasons people try to build very tall. First is ego,” Smith says. “Someone says, ‘I just want to build it, and I am rich enough.’ It is for bragging rights.”

But if there is no limit to human vanity, is there one for skyscrapers? Possibly not. Smith keeps a scale model of a building 1 mile (1.6 km) high that he and his team recently designed. That is almost twice the height of the Burj, or nearly four Empire State Buildings stacked on top of one another. It is hard to imagine anyone living at such altitudes, and Smith says the model was “pure research.” Yet he concluded that if someone is willing to pay billions for it, a mile-high building is feasible.

The major technical challenge for super­tall buildings is wind, which tends to push into structures and accelerate upward­—what engineers call the stack effect. That can cause full-on motion sickness for dwellers on triple-digit floors. To break the vortex, Smith designed Kingdom Tower with a sloping exterior, and the Burj as a series of uneven steps with a Y-shaped bottom. From afar the Burj looks like a thin, jagged stalagmite shooting out of the earth.

The other problem is less obvious: ­elevators. Beyond a certain length, elevator cables have been too thick to spool, requiring people to switch elevators once or twice to reach the top of the tallest buildings, which turns a trip to the lobby into a commute. Yet even that problem could soon be solved. The Finnish company Kone recently unveiled a lightweight, carbon­-fiber rope that will be capable of lifting people all the way up Kingdom Tower in a single elevator ride.

Smith believes the most likely roadblock ahead for even taller towers is not engineering, but money. A mile-high building would have about 600,000 sq m of space, double the Burj. “The biggest challenge would be filling it,” Smith says. “It would need a really thriving economy.” With oil prices down since they dreamed up Kingdom Tower, the Saudis could struggle to sell out their own building. Yet that might not deter others. “If the Saudis have a higher building, then definitely Dubai will make one even higher,” says Abdulaziz Rsheadat, of the Burj Khalifa’s protocol department. “We have to be the world’s tallest.”

The more worrying question is whether the earth can sustain this mania for height. On the one hand, supertall buildings can spur public transportation that might never be built without it; one of Dubai’s rapid-transit Metro lines was completed four months after the Burj opened in 2010. And they also save space by building up rather than out. That’s an advantage in a dense city like Hong Kong or Tokyo, though less so in comparatively empty Dubai. Putting 5,000 tenants in one gigantic tower requires a footprint of about 2 hectares, compared with 12 hectares if they were spread out in three-story buildings. “You can save that land for other uses,” Smith argues. “You can put photovoltaics [solar panels] on it, or wind turbines, or agriculture.”

But the reality is that supertall towers are energy-sucking machines. Keeping the Burj lit and cool takes the equivalent of as much as 360,000 100-watt lightbulbs and about 10,000 tons of melting ice. And although supertall towers save land, they actually waste living space inside. “They are about 70 to 75% efficient,” Smith says. “The rest [of the building] is devoted to corridors and circulation that you do not need in a low-rise building.”

These towers, however, were never meant for efficiency, but rather for awe, and even shock. And so there will likely always be demand for new ones. As the sun sets outside the Burj, Smith leads me into one of its three lobby areas to show me a favorite design flourish: a backlit wall extending about 15 m up, with dozens of smoked-glass panels that send a warm yellow glow up the interior walls of the building when the lights behind them are switched on. The wall is unlit, however. At Smith’s request, building staff scurry around trying to find the right switch. Finally, after about 20 minutes, they find it. The panels light up, and the building glows. But it is a rare treat. “They usually leave it off,” Smith says, disappointed. “It uses too much energy.”

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