Keiko_Mushi
>There was talk of other species than humans. What do you prefer for that aspect of this world? I could create some based on the geographical status of each civilisation...
Well, species wouldn't really be seperated by the levels of the city. Because the way the story seems this city would be less than 100 years old - not long enough for any real adaptations to happen.
There could be a wide variety of species that had "migrated" to the city, kind of like the urban movement thoughout the last century of the US. Or you could base things on the basis of this being an alien planet. Humans came with technology, and they live beneath the city because of harsh solar radiation experienced on the planets surface.
So you could have humans, and some of the planets normal race as the machinists. And the normal race as the religious.
I suggest even though they would be an alien race, that the planets residence be mostly humanoid. Like the races of FFXI. Humans with mild changes to ears, facial structure, and/or size.