One of the most important facts about cities from the beginning of recorded history until the fairly recent past was the sharp distinction between urban and rural ways of life. Within the city wall of most early cities, a visitor would see a dense mass of buildings, congested streets, and a rich and highly dynamic urban life offering many choices, at least for those able to afford them. A few miles outside the walls, however, the same visitor might see nothing but croplands and rural villages. The pace of daily activities would be slower, the environment less quick to change, and social and political life completely different.
In almost every era in urban history, however, there was a transitional zone between the two, a region just outside the city that housed activities and individuals that were still intimately connected with the social and economic life of the city but that couldn't be accommodated easily within the walls. This zone provided space for burial grounds, pottery works, or other industries that were either too space consuming or too noxious to be tolerated within the city itself. It also housed marginal social or political groups and families too poor to afford dwellings inside the walls. In a great many cities, however, this zone also supported activities of a very different sort. Here were the houses of affluent or powerful families who had the means to build and maintain working farms or villas or second houses where they could escape the congestion, noise, contagion, and social unrest that have characterized the center of large cities from the beginning of time until our own day. Sometimes these settlements were permanent, sometimes for seasonal or occasional use. Sometimes they were fairly compact, composed, for example, of small villas surrounded by gardens