A city is the locus of both sociocultural and physical-technical elements in a society. To begin to understand the importance of both kinds of factors, ancient cities are convenient examples to study, especially dead ones that do not “wiggle” under the microscope. By isolating one urban system (water management) we can begin to understand the complication and variability that characterize these early cities, and hence gain insight into the development of other urban systems, as well as the role that water management plays in the evolution of all cities. The received wisdom about the placement of cities usually rates defense as the primary factor, with access to arable land and concentration of trade activities being the other two important factors. A hill top, a protruding ridge, a peninsula or an isthmus between two rivers—all were sites easily defended by walls and hand weapons. Even a broad plain could be utilized if there were a slight rise that could be fortified, such as at the Mycenaean city of Tiryns in Greece. A city on a slight rise in the midst of broad fields of arable and irrigable soil was ideal. Such a formulation leaves out the possibility of deliberately choosing as a site a port city that tapped directly into grazing lands, or the importance of a balance of either fish or meat complementing cereals in the diet. It is more accurate to say that two kinds of food were necessary, either crops and fish or crops and meat. This concept broadens the number and kinds of “ideal” sites. Trade routes, the third factor, also are more complex in form and have more varied effects on urban location than early theories would admit. There are at least three kinds: 1. Overland routes (e.g., the Santa Fe Trail, with its two terminals at Independence, Mo., and Santa Fe., N.M., with Santa Fe being a crossroads where routes from Los Angeles and Mexico City also converged) 2. Land and water interchanges (the north-south land route through France crossing at Paris the east-west river route along the Seine) 3. Water-water interchanges such as New Orleans (Gulf of Mexico and Mississippi River) or Amsterdam (Rhine River and Atlantic Ocean)