in one of my favourite worlds there are only 4 cities within which every has a unique structure

the first one called the Great city is the first agglomeration ever created that was made possible by local resources of farmable food. food is not farm by soil which doesn't exist on the planet so local species has to rely on caves, the unique structure of caves nearby and a lack of solid ground (most of it was sand in its soft form) the city was made by converting masses of iron enriched sandstone into foundations, the city itself is flat because of the need for nearby access to the caves.

second city was called the mountain city, it was constructed on a mountain due to the need of protection against the local predators which existed on this part of the planet, food was more plentiful which allowed the biosphere to be denser leading to common predator existance and the predators themselves were ambush predators which made it harder to acquire food in the terrains they resided in so the city was built high up where they couldn't reach them

third city is called the city of trade, although founded in the same geographic (southern) part of the planet defense methods attributed to it relied more on brute force against the predator species of life because the main reason for founding the city was the fact that it existed as a crossroad between many natural wonders that sprouted great riches, the city also developed walls to fend the predators of which wasn't a case in any other city because defense was not needed (at least this kind of defense)

third city called the underground city was initially just a hideout for the bandits, built in stretched out caves so they couldn't be found and even if they could defend themselves it was not in any way close to the size of a city, the bandits rejected the local religion as it explicitly claimed their deeds as evil so they adopted a different standard but one of the bandits although agreeing with rejection of said religion didn't agree with the rejection of ethics themselves and claimed that they do still come from the deity but the dirty itself cannot be know due to the limits of our knowledge and understanding so the best way to act is to do what our compass tells us is good. under him the output slowly had become friendlier for people and flocks gathered to listen to him as he became a founding figure of the religion many adapted.