I looked into some key points and am including the scan from my neat moleskine:
Water for the city is gathered by rooftop "parks" with plastic bags around the tree branches. The water towers are collecting it and also filter it in a very basic way - rocks, sand and layers of charcoal. Also there are drains around the rooftop for rain water, again filtered in the same way.
Energy/Electricity - i thought of two ways an isolated city like Octavia can gather energy - capturing lightnings, implying the city is very technically developed, or wind energy. Second option seemed more plausible as i don't see the city as very futuristic and "techy".
Transportation - cable cars, simple as that. Public transport is electricity based while individuals have manual cable systems of transportation and lifts to move around the city.
Religion? - i think it is more to do with the spiritual side of the citizens. Since they are high up in the air, between two mountains i can imagine they are quite spiritual. Air as the symbol of intelligence, the people of Octavia have a different understanding of " up and down" (a long and humble curtsey to 2001 space odyssey). They can use lifts to move up and down around the city, they spend a lot of their time hanging in mid air and height is something usual for them.
Houses - hanging tents of course, citizens are growing ivy from their houses that stop them from moving in the wind.
Also I recalled two artists i heard about a few years ago - Dan Havel and Dean Ruck who created a "black hole" house which inspired me for the design for the temple in Octavia. Also there are houses built into the mountains surrounding the city, connected with it by ropes and ladders.
Overall design - the city resembles a scaffolding and the crossed levels and ropes hanging from it vaguely resemble a spider web.
First thumbnail of this new city design is at the bottom of the attached page.
I will do some digital drawings tomorrow, feedback will be welcome.