When an urban unit is constituted by several municipalities, it is defined as a multi-municipality. The municipalities which compose it are either central town, or suburb
If the municipality represents more than 50% of the population of the urban unit, it is the sole central town. Otherwise, all the municipalities that have a population higher than 50% of the most populated municipality, as well as the latter municipality, are central towns. Urban municipalities that are not central towns form the suburbs of the multi-municipality conurbation.
A multi-municipality can be constituted only by central towns.