Santiago Calatrava's soaring World Trade Center Transportation Hub oculus features a wing-like roof which was designed to be retractable. Since the hub finally opened in early 2016, the wings have parted in observance of the September 11th terrorist attacks.

The roof opened at 8:46 a.m. today, coinciding with the time at which American Airlines Flight 11 struck the North Tower. The parted wings provided those inside the hub with a view of 1 World Trade Center. According to ArchDaily:

Following the masterplan laid out by Daniel Libeskind, Calatrava’s design used the angle of light as a guiding principle for orienting the transportation hub - so that at precisely 10:28 am each September 11th (the time of the collapse of the North Tower), a beam of light would pass through the opening in the roof and project all the way down the center of the Oculus floor.

The names of the victims of the attacks are being read this morning at a ceremony at the 9/11 Memorial. You can watch live here.