From a world building stand point, this would be interesting. I (sadly) enjoy the idea of logistics in fantasy. To me, it helps immerse (though probably bores the rest of you!) me in the world because it feels real. My theory is that in the city, most of the food comes from urban farming in found spaces. There is a LOT of green space in there. In the past 700 years since the Darkness hit, the City (and outside communities) have scavenged resources. from the remains of the Golden Ages. I don't think a replicator from star trek or a FLNMRG (Cloudy with a Chance of Meatballs) kind of magic food machine should exist. I think there are still domestic animals in small farms in the city. People will have stuff to eat, but don't count on a lot of fresh meat as a source of protein. Frankly, I would love to know what life is like on the ground level of the city. I love the D&D setting of Eberron and it's setting of Sharn, a multilayered city. I see our City like that. We only see from the top down, and it looks sweet, peaceful, and like something we really want to save. I want to see the nitty gritty. How many people still live in the city? While the walls might be impenetrable to a large scale assault, there are bound to be cracks. How are the Fallen or Hive going about those cracks in the walls? Sorry, off topic =)