In some cases, the urban centre stretches far beyond its boundaries. To better capture the entire urban centre, a 'greater city' level can be created. This is a fairly common approach and several greater cities have already existed: Greater Manchester, Greater Nottingham etc. This level was created for some capitals and several other large cities. Based on the new clusters from the 2011 population grid, several new Greater cities were defined – for example, Madrid, Valencia, Sevilla, Elda, Granada, Puerto de la Cruz, Santa Cruz de Tenerife, Pamplona/Iruña and Igualada in Spain.
In some cases, the greater city contains a single city. Athens is a clear example of such an approach. The urban centre (in black) is much bigger than the city (in red on the map). A greater city level was added (blue outline), which captures a far greater share of the population of the urban centre.
Some greater cities include multiple cities. In most cases, the greater city equals the combination of two or more cities. The greater city of Porto, for example, is made up of five cities (Porto, Vila Nova de Gaia, Gondomar, Valongo and Matosinhos). In a few cases, the greater city includes several cities and other communes, as for example in Rotterdam, Helsinki, Milan and Naples.
