Never been done before. These portals exist throughout Prey. Walked through a portal. Looking up through water at what's above. To further show what portals can do, we were shown a room with portals on every side.
Portals are jumps, in a sense, from one space to another.
They can exist next to each other, behind each other, anywhere. I won't even try to properly explain them, but just remember this. The world of Prey is NOT as it seems. We were shown a cinematic from the game, where Talon is told by his dead grandfather about his history. The camera was zooming in on faces, panning the area, much as real directors do in film.