Chapterhouse is the term used by the Bene Gesserit for the planet considered to be their home base. This planet has changed over the centuries of the existence of the Bene Gesserit. Speculation would put the original Bene Gesserit home base on the planet Rossak. The planet used as the secret headquarters of the Bene Gesserit is seen as a temporary base, and because of this the planet is never quite 100% settled and if needed, the Bene Gesserit can completely abandon the planet in very short notice leaving very little trace of their time spent.