updated 01:25 pm EDT, Thu August 28, 2014
Purpose so far unknown
A "massive structure" is being constructed on the campus of the Flint Center for the Performing Arts in Cupertino, the site of Apple's September 9 press event, witnesses say. The structure is encased in a white barricade, and appears to be about three stories tall. "Scads" of security staff are reportedly protecting it, and administrators will only say that they "are not at liberty to discuss that [structure] due to client wishes."
Construction has been underway since before August 20 (the date the included photo was taken), but appears to have gone unnoticed, since Apple usually prefers to host events in San Francisco or at its own headquarters. It's unclear how the structure might fit into Apple's event -- if it is indeed related -- but it might be used to shelter product demonstrations, or other temporary needs, such as press overflow.
The structure could also have something to do with recent rumors that have the company also introducing the iWatch at the September 9 event. Since the iWatch is a health- and fitness-oriented device, an outdoor space could be essential for letting media try it out.