There seems to be two different forms or experiences of space.
One is the space we experience when there is an overlay of images of physical 3D space. This is what we use to navigate in the world, or explore 3D space in our imagination. This is how space appears when the 3D overlay and the objects within the space is emphasized and focused on.
Another is the space we experience without this overlay, or where this overlay is lighter and more transparent. This is a space that’s boundless, since any boundaries are literally imagined and happens within this space. This is how space appears when the space itself and its boundlessness is noticed.
It can be very helpful to notice the latter space. Notice that even the strongest bodily or mental contraction happens within space, and that this space is – quite literally – boundless. It makes it easier to meet the experience of contraction, rest with it, and perhaps see what’s there with gentle curiosity.