When people began concentrating in cities, their governments became more structured and formalized as well. At an early stage, the ruler of the city established headquarters buildings where the business of running the city was conducted: citizens were interviewed, edicts were issued, taxes were collected and stored, and diplomacy was carried on. In many cases, these seats of governmental power also served as the living quarters of the ruler. In cities that were sufficiently wealthy, these headquarters often became PALACES, immense and imposing structures that were a source of civic pride, and which reinforced the aura of power attached to the ruler.