Describe Ember. What are some important aspects of the city?

Ember is the setting of Jeanne DuPrau's 2003 science fiction novel. The city is an underground refuge in a post-apocalyptic world, and perhaps the most important characteristic is the electricity. All the citizens of Ember have only ever known the lights that define their days instead of the sun—in fact, they don't even know they're living in a city built to survive the apocalypse. To them, it's just home. The city incorporates a river, which powers the generator. One of the main characters, Lina, "knew about the generator, of course. In some mysterious way, it turned the running of the river into power for the city" (67). It has been so long since the inhabitants of Ember first settled in the underground city that all they know is that there is a generator and a river, and somehow the two power their entire lives.
Being in such a contained space for over two hundred years, there's bound to be some conflict. Although it doesn't seem to be a conflicted place, the city still has some physical characteristics of the power structure in the architecture:

The mayor's office was in the Gathering Hall . . . And there were offices for the guards who enforced the laws of Ember, now and then putting pickpockets or people who got in fights into the Prison Room, a small one-story structure with a sloping roof that jutted out from one side of the building. (62)

Here, the reader can see that the Mayor's status is reinforced by his office being in what is presumably the most central location. The guards are an extension of the Mayor's reach; therefore, they also have offices in that central location. The prison being only a room tells the reader two things: firstly, that the control of the mayor is fairly absolute (especially in that the worst infractions are pickpocketing), and secondly, that it's possible the Prison Room was an add-on that the Builders hadn't thought necessary, pointing to the issues surrounding a population trapped in a very small area.