The Oculus (WTC Transportation Hub) is a real time commitment — fit it in only if it's a priority.
Allow 15–30 min.
Calatrava's white skeletal ribcage floods with light through its spine skylight — and the moment to be standing under it is around solar noon, when the sun lines up with the long central skylight and the whole spine glows. Free to walk through, and the pairing that makes it worth more than a photo: enter from the 9/11 Memorial side so you arrive at the somber reflecting pools first, then step into the soaring light of the Oculus — the contrast is the point. Beneath the drama it's a high-end mall, so it's a 10-minute architectural wow, best stitched to the memorial rather than visited alone.