Terran's Ponderous Campaign
Prospolis is a coastal city, and the capital of the ancient, nearly defunct Anatan Empire (Famous to the point of synonymous with convoluted, deadly politics). In contemporary times, the Empire has shrunk to roughly a days ride in any direction from Prospolis.
The name “Prospolis” is nowadays often used (by those outside the Empire) to refer to both the city and the Empire itself, much to the irritation of actual Prospolans, and Anatans as a whole.
Despite its waning fortunes over the years, Prospolis itself still retains quite a bit of weath, and some influence over the region. Its location at the end of the Chain Lakes trade routs; opening onto the Mare Mercuria guarantees that the city will have a hand in all trade in the area.