One thing almost every Orbital - whether just two Plates or a completed ("closed") Orbital - does have, is a Hub. As its name implies, the Hub sits in the centre of the Orbital, equidistant from all parts of the main circumferential structure (but not physically joined to it, normally). The Hub is where the Orbital's controlling AI (often a Mind) usually exists, running, or helping to run, the Orbital's transport, manufacturing, maintenance and subsidiary systems, acting as switchboard for trans-Orbital communications, library and general information point, traffic control for approaching, departing and close-passing ships, and generally working as the Orbital's principle link with the rest of the Culture. During the construction phase of a Plate-pair, the Hub will normally control the process.
- A Few Notes On The Culture