‘Not that,’ Asher said. ‘It’s all about distorted spacetime, Chinelo. I think this structure, and maybe the Deck Three wormhole too, is like a tesseract. A four-dimensional cube. You know the idea? On a softscreen you can draw a square, in two dimensions. Print out six squares and you can fold them up and over to make a cube, the two-dimensional surfaces surrounding a three-dimensional space. And similarly, if you print out eight of those cubes, you can, in theory, fold them up into a fourth dimension. You get a hypercube, with eight faces – each of them an ordinary three-dimensional cube – enclosing a four-dimensional volume. When you were walking through the Rooms, you were walking over the three-dimensional surface of a four-dimensional hypercube. You were like ants crawling over the surface of a box – but never noticing the ninety-degree tilts where one square face joins the other, and never seeing the interior.’
-Xeelee: Redemption, Ch. 72