The excavation, besides providing the foundation for this enormous construction, would house parking garages, subway terminals and tubes, and shopping concourses.
To minimise disruption, the new concourses will be built first, allowing them to take over operations from Terminal 2 when the existing building is demolished.
Inside, a dramatic staircase floats diagonally through what Bjarke Ingels describes as 'a single confident volume' akin to Kings Cross station's magnificent multi-arched concourse.