In the study of human settlements, an urban agglomeration is an extended city or town area comprising the built-up area of a central place (usually a municipality) and any suburbs linked by continuous urban area. INSEE, the French Statistical Institute, uses the term unité urbaine, which means continuous urbanized area. However, because of differences in definitions of what does and does not constitute an "agglomeration", as well as variations and limitations in statistical or geographical methodology, it can be problematic to compare different agglomerations around the world. It may not be clear, for instance, whether an area should be considered to be a satellite and part of an agglomeration, or a distinct entity in itself.
The term agglomeration is also linked to conurbation, which is a more specific term for large urban clusters where the built-up zones of influence of distinct cities or towns are connected by continuous built-up development (Essen - Dortmund and others in the Rhine-Ruhr district), even in different regions, states or countries, (Lille - Kortrijk in France and Belgium). Each city or town in a conurbation may nevertheless continue to act as an independent focus for a substantial part of the area.
The term "agglomeration" is more appropriate for determining the populations of large super-cities like Tokyo, New York City, Mexico City, Delhi, and Seoul. These examples are super-cities which have expanded enough to consume other neighborhoods. Although administration may be separate for outlying districts, the population might say they are from the central city.
The 25 largest agglomerations by population in March 2013, according to Demographia:
|6||Manila (Mega Manila)||Philippines||21,241,000|
|8||New York City||United States||20,673,000|
|17||Los Angeles||United States||15,067,000|
- World's largest cities - A list of the largest municipalities (cities) areas by population
- Metropolitan area
- Transborder agglomeration
- Urban sprawl
- Global city
- Economies of agglomeration
- United Nations World Urbanization Prospects, the 2009 Revision, Web Site of the United Nations Population Division: Data on Urban Agglomerations
- e-Geopolis project Research Group, University Paris-Diderot
- Principal Agglomerations of the World