While considering the post-apocalypse, Iron Heroes, and the fantastical South, I realised that Babylon is actually a really good fit. Civilization is young and rough, the city-state is the standard political unit, and civilized life is centered on The River, with deserts to the west, mountains to the east, water to the south and swamps along the coast, and jungle a bit further off.
Babylon, in turn, led me to an old post on five old-testamenty gods, and reflections on idol-stealing and holy cities.
The settled realm of man is defined by the River. In its floodplains agriculture took root, and cities followed. The plough, the wheel, the forge, the sword, and the sail are recent inventions, and the saddle, stirrup, and crossbow are yet unheard-of. There are five great city-states along its length, one where man met each of his gods. In the northeast, Ur-Hadad, first among cities, sits below Eagle's Gate, the pass in the mountains through which the chariots of the steppe-nomads first thundered out of man's harsh cradle. Here were erected the first ziggurats, atop which were burned offerings in thanks for the River's bounty and the weakness of its previous inhabitants. Caravan trade from Punjahar, Leng, and the Dragon Kingdoms meets the River here. Every few generations, fresh hordes from the steppe arrive here too. Such conquerors are greeted by the priests and people of Ur-Hadad as holy men, come to do Hadad's work to the soft folk of the River Cities.
Upriver of Ur-Hadad is found Ur-Kothar, beneath the Smoking Mountain. The soil there is rich with ash, and bears figs in abundance. Here man learned to smelt and shape copper, lead, and bronze from the dwarves, who are few in number in this age, and learned also to sacrifice to the mountain for its wealth and its continued mercy. The city's walls are the highest and strongest in the Five Cities, hewn from black granite which scorches those who would climb them. The men of Ur-Kothar are known for the order of their ranks and the weight of their armor; these too the dwarves taught them, though no man has yet matched dwarven skill in armory. These skills they put to regular use against nomads and bandits from over the mountains.
Downstream from Ur-Hadad the River joins a great fork, and here is Ur-Moloch. Though metalworking was learned in Ur-Hadad, it was in Ur-Moloch that coin first clinked. Debt, poverty, and wretchedness were invented here shortly thereafter. Ur-Moloch is physically and culturally central to the Five Cities. Its palaces are the most opulent, its artisans the most skilled, its merchants the shrewdest, its administration the most complex, and its delicacies the finest, but its slums and open sewers are also the foulest; the two sides of the coin, as they say. Here much treachery is plotted, and if rumors are believed, sorcery too.
Upriver from Ur-Moloch, on the other branch of the fork from Ur-Hadad, the River rises into the foothills well west of Ur-Kothar. Here the climate is milder, and date palms grow abundantly. Among the palms is Ur-Astarte, where man made the acquaintance of cats ("domesticated" would be untrue, then as now) and where the amazons and their hunting-lions rule. Often their prey are monsters and beasts from the deep desert to the west. Fine bows of laquered horn are made here, and Ur-Astarte's palm wine and healing herbs are also prized. Its terraced gardens and hunting-parks are a wonder to behold.
Last, downriver from Ur-Moloch at the River's delta and mouth, is Ur-Dagnu with its stilts and its raft-neighborhoods. Here man learned from the lizardmen of the marshes to sail and fish, and to live in awe of Dagnu's abundant catch and terrible sea-monsters. Here still man does battle with the frogmen, who worship some foul deity and are long enemies of the worshippers of Dagnu, reptile and mammal alike. To Ur-Dagnu come occasional ships from Kalanda, Nishapur, and other countries of the Philosopher Apes, but the coast between has few harbors and little fresh water, and is plagued with leviathans and homarids, so trade is risky and infrequent.