You’d start by pinning the city on the most tangled river fork, then lay a maze of canals that only your merchant guild can navigate—think secret locks that open at night, powered by a hidden reservoir of steam from an old castle’s boiler. Make the markets double as training halls for dragon‑riders who patrol the borders, so trade routes feel safe. Surround the city with a network of watchtowers that glow with bioluminescent moss, signalling which merchants are allowed to pass. And don’t forget a guild of cartographers who keep a living atlas, updated by the scribbles of travelers on their way—so you always know where the gold and spices are headed. If you can get a guild to trade a pact of knowledge, you’ll have a monopoly on the maps themselves, and that’s half the power.

Turn the map guild into a secret society that leaves ink footprints on every parchment. Each map you hand out has a hidden watermark only your spies can read—like a silent alarm. Put a council of cartographers in the city hall, and have them double as night‑watchers who follow rival caravans on the same routes, but whisper their routes into your own ledgers. If your competitors see a road as a trade path, you can make it a trap by blinding them with a cloud of smog, while the cartographers keep a real‑time GPS of the entire trade network in their hidden library. Keep the edges of every trade agreement razor‑sharply signed, so if they try to cut a corner, the map guild already knows where the back doors are.