Check out the design proposal by SOM for a 'hovering' UFO over New York's Grand Central Station... pretty amazing:
Their scheme would install a circular pedestrian deck far above the surrounding buildings, suspended between two new commercial towers. The deck would be open 24/7 and rival the Empire State Building for views. Below it, plenty of POPS (privately-owned public spaces) would add green space at ground level. Here’s the kicker: it moves. Suspended like a crown above the neoclassical facade of Grand Central, the circular tubing would move upwards to give visitors varying views. “This grand public space moves vertically, bringing people from the cornice of Grand Central to the pinnacle of New York City’s skyline,” explains SOM partner Roger Duffy. Details on the structure are hazy, but renderings imply that two massive trusses would support the donut-shaped platform, hooked into vertical notches--not unlike some window-washing mechanisms.