Bird's-eye View Aerial City Landscape Photography

Cities generally have complex systems for sanitation, utilities, land usage, housing, and transportation. The concentration of development greatly facilitates interaction between people and businesses, benefiting both parties in the process. A big city or metropolis usually has associated suburbs and exurbs. Such cities are usually associated with metropolitan areas and urban areas, creating numerous business commuters traveling to urban centers of employment. Once a city expands far enough to reach another city, this region can be deemed a conurbation or megalopolis.
Origins
There is insufficient evidence to assert what conditions in history gave rise to the first cities. Theorists, however, have speculated on appropriate pre-conditions and have identified some basic mechanisms that might have been the important driving forces.