On each beginning of the game, the city is randomly generated. This makes for a new experience every time a new game is played which keeps things fresh for the player.
Probably not for everyone, but if you like a zombie overrun post-apocalyptic scenario, this game sets the atmosphere accordingly with constant scavenging for resources on the verge of human extinction, moral choices and a disturbing soundtrack.
Rebuild tends to get easier the more farmland one obtains, so the further the player reaches in the game the easier things become, which looses some appeal.