Umm... our Calatrava "flaps"?

The [WTC Transit] hub's ceiling has been designed to open to the sky using hydraulic motors on Sept. 11 and on other days the Port Authority designates. That feature is similar to Calatrava's design for the Milwaukee Art Museum, which 'flaps' its wings every day at noon.

Newsday.com :: WTC transit hub design steeled, yet still light