ew York City is famous for its dynamic skyline filled chock-a-block with imposing buildings that seem to kiss the sky. These monster structures might appear as solid and staid as granite, but, in fact, they are built for flexibility.

"If they don’t bend, they break," says Albert Elmuza, Resident Manager of the 73-floor CitySpire, located at 150 West 56th Street.

Residents who live in some of the city’s tallest buildings don’t always perceive the motion, but some people can get motion sickness on especially stormy days when winds whip upwards of 30 m.p.h., causing the buildings to shake and shimmy.

One tenant at CitySpire who declined to be named, remembers one day last winter when he saw the water in a glass on his kitchen counter rocking back and forth. “I got so nervous, I headed straight for the door and went to the lobby downstairs,” he says.

Mark Edwards, a doorman at CitySpire, says that during the worst storms some nervous residents come to the lobby to wait out the storms. “They do get some toilet water sloshing around and that sort of thing,” he says.

At 814 feet, CitySpire is the tallest residential building. But not for long. The Trump World Tower, which is currently being constructed, is about to inch out CitySpire to become the tallest residential building in the world at 70 stories, or 861 feet — just 47feet higher than CitySpire. The massive shimmering tower is designed in classic — read flashy — Trump style. Its exterior shimmers like a massive mirror and the apartments are all laced with gold faucets and light fixtures.

he Trump building, just a block away from the United Nations on the Upper East Side, has been surrounded by controversy over its massive size, which will block the world class view for many of its neighbors. But a lawsuit brought by a coalition of neighborhood and civic groups was dismissed after a judge found that no zoning laws were being violated.

The massive Trump Tower, now built up to the 41st floor, will sway one foot in either direction according to Kevin Murphy, vice president of Bovis, the company overseeing the construction of the building. To counter the sway, the top of the tower will contain a 600-ton steel “tuned mass damper,” — a kind of giant pendulum that counters the movement of the building.

"It doesn’t as much reduce the sway as it reduces the acceleration of the sway," says Murphy, "so people don’t perceive the sway as much. We don’t want the people at the top to get seasick."

In the past, people have experience nausea from swaying buildings. The old Gulf and Weston building at the corner of Central Park West and Columbus Circle used to sway so much that "on a windy day, you could see people coming out blue and green, getting sick," says Christian Meyer, professor of engineering at Columbia University. The building has now been remodeled by Donald Trump.

Of course, people buying the luxury Trump apartments surely won’t stand for seasickness in their own homes "I think the comfort issue becomes more important because people are actually living here as opposed to working here from nine to five," says Murphy, "People will essentially be here 24 hours a day. And, of course, the people living at the top of the building will be paying premium dollars for those apartments, so we want to make sure they will be comfortable."