Welkinstead

Welkinstead is the innermost of Focus's two gas giants. (Or if you want to be pedantic, it's the only gas giant, with Moonlitter being an ice giant.) Its atmosphere is rich in economically exploitable gasses. Terraforming proceeded slowly, with floating extraction platforms similar in function to oil rigs being built in the layer of atmosphere where the gasses are most abundant. These structures are held aloft by vacuum pontoons and are capable of a small degree of self propulsion, but otherwise float along with the jet stream. Over time, these floating gas rigs slowly expanded or grouped together until they became floating cities, with entire economies that support the workers who extract the gas.