Cities and towns have been established to fulfill central functions in the production, exchange and consumption of commodities, as well as to serve as administrative and religious centers for a certain district, region or realm. Therefore, they are characterized by populations larger, denser and more complex than that of the surrounding countryside. In order to manage this complexity efficiently, cities were given or gradually acquired a certain degree of autonomy and developed their own governing bodies and institutions, with varying degrees of participation by inhabitants of different social and legal standing. The system of governance necessitated the use of administrative literacy and the appropriate shaping of the physical environment, including its open spaces, buildings and ornaments.