Remember the bar in Star Wars? Read about the Hotel Universe, Lunograd, on pp. 359-360 of David Falkayn: Star Trader. Chee Lan's rooms have crisscrossing bars not only for exercise but also for moving around. Did you know that there was an Epopoian Empire in the Technic History? It has an Ambassador to the Solar Commonwealth and he caws through a beak. That is all that we are told about him. Chee Lan knocks him over in a hotel corridor so his only purpose in life is to emphasize to the reader that she is in a hurry.
The Epopoian Empire could be an interstellar realm or it might occupy just one part of a planetary surface? There must be many realms, large and small. In a multi-species scenario, the author can invent a new one just as a minor background detail.