The Brazilian metropolitan regions were created by a law passed by the National Congress in 1973, which defined them as "a set of contiguous municipalities and socioeconomically integrated with a central city, with public services and common infrastructure."
In Brazil, some metropolitan regions are more articulated than others. Historically, it is noticeable that the southeast and the south are regions whose articulation process is increasing and with definite purposes.
In Brazil, thirteen metropolitan regions are legally recognized. Two of them, São Paulo and Rio de Janeiro, are national. The other eleven cities, Belo Horizonte, Porto Alegre, Recife, Salvador, Fortaleza, Curitiba, Belem, Baixada Santista, Vitoria, São Luís and Natal, are considered regional, since they exert their polarization power only on a regional scale.
The metropolitan regions with the largest number of municipalities are:1st Sao Paulo (39)
2nd Belo Horizonte (34)
3rd Porto Alegre (31)
Urbanization reaches:89% in the United Kingdom
78% in Japan
77% in the United States
80% in Brazil
According to the IBGE, cities are classified into:Global metropolises, national metropolises, regional center, subregional center 1 and subregional center 2.