k_raso's comment gave me an idea. Why not change the appearance (and visible name) of the "palace structures" for certain cultures. Should not the greeks have a hill with temples in the center of the city. And the center of a roman city was its forum. For example, the romans could have a forum building as the center of the town, represting the government and social part of the forum, and a market building represent the trade and game-based bonus of the forum.
As well as the fact that democratic and republican western cultures didn't have a huge single residence in the center of their cities.