ESPON metropolitan areas in the United Kingdom

A 2001 ESPON metropolitan area was defined as consisting of an urban area, conurbation or agglomeration, together with the surrounding area to which it was closely economically and socially integrated through commuting. The European Union's ESPON (European Spatial Planning Observation Network) project defined a harmonised series of metropolitan areas across Europe, made up of two components: Morphological Urban Areas (MUAs), which were similar to urban areas that form the densely populated urban cores of metropolitan areas, and Functional Urban Areas (FUAs), which form the labour basin surrounding Morphological Urban Areas.

Source: Wikipedia — ESPON metropolitan areas in the United Kingdom (CC BY-SA 4.0)