Waterslide arrives on top of downtown Chicago office building

The rooftop of a downtown building in downtown Chicago just got a curious addition built this morning. A white bulbous alien ship/water slide just landed down on top of the Realtor Building on 430 North Michigan Avenue. I work on the 14th floor of the Tribune Tower, so it gives me great curiosity what this thing will be, so I emailed the owner of the building, the National Association of Realtors:

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This morning I noticed the new construction on top of your building at 430 N. Michigan Ave, Chicago. I am an employee of Tribune Company right across the street from you, and I am curious what that new construction will be on top of your roof. (Don't worry, I'm not anyone official representing the Tribune company. I'm just a curious fellow neighbor).

We have several theories about what it will be. 1) It will be a rooftop garden. Chicago loves its rooftop gardens, so it makes sense that the National Association of Realtors would decide to go green on its property. 2) Waterslide. The white tubeous shape resembles a water slide. Can you imagine the fun sliding around in a water park on top of a downtown Chicago building? 3) Roller coaster. Again, that would be great fun. Will you charge admission? 4) Alien welcome center. The tall sharp spires look like some sort of calling beacon for passing-by aliens. The white rounded arching metal shape resembles an alien ship alerting aliens that is it safe to land there. If this option is indeed true, then it was great foresight on your part, because when aliens invade our planet, they will inevitably need a place to live and work. What greater place to start than the National Association of Realtors?

So those are our four theories so far for what the construction will be on top of your building. Any clarity in this matter would be greatly appreciated. Thank you.
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