This giant building has no windows or doors; Its only connection to the outside is an input of energy.

Inside, an ecosystem made entirely of women is sustained by machines, operated and maintained by the women. They are constantly being slaughtered, some willingly, some not, so that their bodies can be taken apart and put to use. Some parts are simply cooked and eaten, some tissues are grown on chemicals produced with the energy from outside, some are frozen.

The wombs and milk glands are usually kept alive; The former to grow new women, the latter to produce more diverse food. They are born on the cusp of adolescence, and it doesn't take long before they can be taught a profession and the ways of the world.

Although there are many women alive at any one time, the mass of flesh harvested from them is much greater. The milk glands would simply die if kept too long(they eat them first), the grown tissues can only grow so much, the chemicals produced by the machines can't be eaten; So everyone's survival depends on maintaining the bloody cycle.