Still a work in progress, expect to be seeing more soon.

this is really just the most crude design of how I want the gears to look.
The city is divided in the under and upper "gearers". Two different races, living in the same city, but rarely contacting eachother, yet the whole system relies on how they maintain their magic crystals. This means half of the city buildings will be made upside down at the underside of each gear. 

The lore:

Once there was a prosperous isle, rich mines, fertile lands and a hospitable climate, it was all there. The people on the isle throve for many a century... growing more skilled in technology and magic. By the end of the eight century, the height of the kingdom, it all changed. They had grown arrogant and lazy, with too much power for them to tap in. First the harvest started to become less and less, then the winters grew cold and harsh... and in the end even the dead could not lay in peace.
The magic they had tapped in was that of the isle itself, that which had kept it a lush and prosperous paradise for so many ages. It was all wasted into the air, the magic that made life so easy. Using the last magic there was deep in the core of the isle, a bold design was made: a machine to retake the magic that was lost, dilluting it back from the very air itself. Within 50 years the project was complete, but the use of this last bit of magic had made life impossible on the isle. The humans fled onto the gears of the machine, half on the upper side, and half to the underside. The gravity created as a byproduct of the floating crystals that send life back into the ground kept them to their gears, unable to switch sides.
It took so long for the machine to start having effect, centuries. In the meantime each gearside was exposed to the magic from the crystals,  transforming the humans on it. And as the upper and undergearers were created, the communication was lost between the two halves.

The uppergearers were exposed to light, and harsh cold, in combination with a crystal that send out light magic itself. They grew white fur and tails to keep them warm and protect their skin, and even their eyes turned light to allow them to see in this bright world. The upper gearers hearts where filled with the order and strength of the light, but it took the warmth out of them. The upper gear is a harsh world of order and light...
On the contrary are the undergearers, who had to deal with an eternal twilight, in combination with the crystals of darkness. They grew pale skin, big, dark eyes, and as they were exposed to monsters, they grew claws so they could always protect themselves. The crystal of darkness made their souls chaotic but intelligent, but it took away all sense of day and night, all sense of time itself, making them as carefree as could be.


The other side of the gears are only legends for each side, the uppergearers are hairy, brutal werebeings in the legends of the undergearers, and the undergearers are dangerous witches in the eyes of the uppergearers. As long as each side maintains their crystal though, life will be restored to the isle, but that might take centuries, if not millenia... perhaps they'll even forget why they restored life at all, just like they forgot the other half of their civilisation.

Right now I am planning on finishing this gear, and adding a few (5 or so) smaller gears with farms/communities. Perhaps I will add one similar big gear if I still have time left after that.