Every September 11, the roof of the new World Trade Center transportation hub (the giant white building downtown that looks like a bird) will open to the elements for a symbolic 102 minutes. 
“That is how long the 2001 terrorist attack lasted, from the time the first jetliner hit the trade center at 8:46 a.m. until the collapse of the second tower at 10:28 a.m,” The New York Times reports. 
The still-incomplete hub’s 355 long skylight, which measures 12 feet at its narrowest and 22 feet at its widest, is designed to retract open and allow the elements to penetrate the space.
The goal of this opening is to allow people to experience the “subtle sense of man's vulnerability,” Santiago Calatrava, the hub’s designer said. 
The transportation hub has been under construction since 2006 and has been mired in controversy. The project, which has a $3.9 billion price tag has been criticized for its design, extreme delay in construction and dramatic cost. 
The hub is scheduled to open this year in December.