5. Original Plans Had a Retractable Roof

In a plan the New York Times called “exorbitant,” the roof of the Oculus was originally meant to retract. The two “wings” would have opened up to 50 feet, like a Venus flytrap, and Port Authority officials even went to the Milwaukee Art Museum to see Calatrava’s retractable roof in action there. The idea was nixed, after three years of debate, due to cost-cutting measures but the skylight panels on the spine of the World Trade Center Transportation Hub do retract.

Every September 11th, the panels will open for 102 minutes, the amount of time between when the first plane hit the World Trade Center and the collapse of the second tower in 2001.