Well, assuming that the place has things like restrooms and showers included, I would thing a place to house livestock. If that is included in the 'food growing facilities', then I also think a library would be wonderful. An exercise room might be needed as well, to keep the underground dwellers physically healthy.
Maybe a rec room that has a library, exercise equipment, games, art supplies, etc. Yep, that is my answer, a recreation room. :)