A city is an urban area with a high population density and a particular administrative, legal, or historical status.

Cities generally have advanced systems for sanitation, utilities, land usage, housing, and transportation and more. This proximity greatly facilitates interaction between people and businesses, benefiting both parties in the process. However, there is debate now whether the age of technology and instantaneous communication with the use of the Internet are making cities obsolete.

A big city, or metropolis, may have suburbs and regions. Such cities are usually associated with metropolitan areas and urban sprawl, creating large numbers of business commuters. Once a city sprawls far enough to reach another city, this region can be deemed a conurbation or megalopolis.

The birth of cities

There is insufficient evidence to assert what conditions in world history spawned the first cities. Theorists, however, have offered arguments for what the right conditions might have been and have identified some basic mechanisms that might have been the important driving forces.

Cities or agriculture first?

According to Vere Gordon Childe, for a settlement to qualify as a city, it must have enough surplus of raw materials to support trade . Bairoch points out that, due to sparse population densities that would have persisted in pre-Neolithic, hunter-gatherer societies, the amount of land that would be required to produce enough food for subsistence and trade for a large population would make it impossible to control the flow of trade. To illustrate this point, Bairoch offers an example: "Western Europe during the pre-Neolithic, 1 the density must have been less than 0.1 person per square kilometer" . Using this population density as a base for calculation, and allotting 10% of food towards surplus for trade and assuming that there is no farming taking place among the city dwellers, he calculates that "in order to maintain a city with a population of 1,000, and without taking the cost of transportation into account, an area of 100,000 square kilometers would have been required. When the cost of transportation is taken into account, the figure rises to 200,000 square kilometers..." . Bairoch noted that 200,000 square kilometers is roughly the size of Great Britain.

In her book The Economy of Cities, Jane Jacobs makes the controversial claim that city-formation preceded the birth of agriculture. Jacobs does not lend her theory to any strict definition of a city, but her account suggestively contrasts what could only be thought of as primitive city-like activity to the activity occurring in neighboring hunter-gatherer settlements. To argue this view, Jacobs suggests a fictitious scenario where a valued natural resource leads to primitive economic activity—in her example, the resource is obsidian. The stock of obsidian is controlled and traded with neighboring hunting groups. Hunters that do not control the stock travel great distances to barter what they have, valuing obsidian because it "makes the sharpest tools to be had" . This activity brings more people to the center as jobs are created and goods are being traded. Among the goods traded are seeds of all different sorts, stored in unprecedented combinations. In various ways, some accidental, the seeds are sown, and the variation in yields are observed more readily than they would be in the wild. The seeds that yield the most grain are noticed and trading them begins to occur within the city. Owing to this local dealing, the city dwellers find that their grain yields are the best and for the first time there is deliberate and conscious selection. The choices made now are purposeful, and they are made among various strains of already cultivated crosses, and their crosses, mutants and hybrids .