‘The whole of this “city” is a Xeelee artefact, of course. We seek small, portable devices. I’ve only ever seen two kinds. Two, in a thousand years.’ She patted one pillar. ‘One type is associated with pillars like this. You always find them in such rooms, sitting on pillars, facing each other. Hoops, each maybe half a metre across. Sky blue, polished – paper thin – and before they’re detached from the pillars you can see pink sparks dashing around the circumference. They go inert when removed, as they have been from this place, as you can see. The Ghosts think they are some kind of comms device.
-Xeelee: Redemption, Ch. 17