My ID classmate kept getting burgled. His second-storey East Village apartment was broken into multiple times, and in frustration he signed a year lease on apartment 6B of a six-flight walk-up. He reasoned that no thief would be willing to haul a television down six flights of stairs. But within a month, he was robbed again—this time they broke in through the roof door. And my TV-less buddy spent the next 11 months going up and down six flights of stairs every day.

Six storeys (some say seven) was the maximum height they'd build residential buildings in New York, prior to the elevator. No resident was willing to climb more stairs than that. After Otis' perfection of the elevator, that height limitation was gone, and within a century we had skyscrapers. Then the new height limitation was building technology.

Advanced construction techniques have since skyrocketed, if you'll pardon the pun; as the World's Tallest Building peeing contest continues, it is rumored that Saudi Arabia's Kingdom Tower will be a kilometer high. But the new height limitation is the thing that smashed the old one: Elevators. Steel cable is so heavy that at its maximum elevator height of 500 meters, the cables themselves make up 3/4s of the moving mass. You can stagger elevator banks to go higher, but the heaviness of steel cable makes long-haul elevators prohibitively expensive to run.

Finnish elevator manufacturer Kone believes they have the answer. After ten years of development they've just announced the debut of UltraRope, a carbon-fiber cable that's stronger than steel, lasts twice as long, and weighs a fraction of the older stuff: