An urban area, built-up area or urban agglomeration is a human settlement with a high population density and an infrastructure of built environment. This is the core of a metropolitan statistical area in the United States, if it contains a population of more than 50,000.
Urban areas originate through urbanization, and researchers categorize them as cities, towns, conurbations or suburbs. In urbanism, the term "urban area" contrasts to rural areas such as villages and hamlets; in urban sociology or urban anthropology it contrasts with natural environment.
The development of earlier predecessors of modern urban areas during the urban revolution of the 4th millennium BCE led to the formation of human civilization and ultimately to modern urban planning, which along with other human activities such as exploitation of natural resources has led to a human impact on the environment.
[...] the Bronze Age, starting between 3500 and 3000 BC [...]. During this [...] period the first urban civilizations were firmly established.