While one might think of the public realm as any and all space outside one's front door, the reality has never been as simple. Throughout history, different activities and philosophies have shaped the ways societies interact with public space, which has in turn contributed to the ever-changing state of public architecture and public space planning. Even in the modern day, the public realm is ill-defined, and really exists as more of a spectrum from public to private. Though many activities once thought of as public have moved into the private domain, cultural differences and the differing urban character of cities continue to contribute to sometimes massive differences in how the public realm is regarded between nations or even nearby cities. These differences that develop throughout place and time cannot be attributed to one single law or idea, but rather a collection of factors. The public life of cities is shaped as much by the decisions of government officials and city planners as it is by the ways people simply choose to interact with the public realm. Social interaction, political demonstration, religious life, cultural events and exchanges, commercial transactions, and environmental quality all contribute in major ways to how the public perceives the public realm, and how designers design for it. In examining societal views of the public realm, it is of the utmost importance to examine how these factors have contributed to the shape of the public realm over time. The public space of an ancient Middle Eastern city, will be different from that of a medieval European city, which will in turn be different from a cosmopolitan western city, but ideas from all times and eras will undoubtedly still be reflected in the modern shapes and perspectives of the public sphere.