The 'undersides' of the Wards, between the inhabited superstructures and impenetrable outer hull, and called the Foundations. These dangerous areas are filled with life support systems and power plants. Officially, only the keepers are allowed in the Foundations. In reality, the Foundations are the slums of the Citadel, home to criminals, minorities, transients, and occasional 'state-less' exiles. Some stay in the Foundations of their own will. Others end up there when the opportunities they sought in the Citadel do not come.
The stations recycling systems are located in the Foundations. These manufacture a variety of artificial organic pastes that can be eaten for sustenance. They are free and nutritious, but nearly tasteless and of unpleasant texture. Poorer Citadel residents quickly become adept at dressing up this bland fare with sauces and spices, while imported foodstuffs are a popular luxury of the wealthy.