Four cities can be replaced by various synonyms depending on the context of use. For example, if one is referring to four cities in a certain state, they can be called a quartet of urban areas or a quadruple of municipal centers. In the case of discussing common tourist destinations, a tetrad of popular cities can be used. Alternatively, if the focus is on addressing the unique characteristics of the cities, one can opt to use a collection of distinctive urban centers instead. Other possible synonyms include four metropolises, a group of metropolitan areas, four significant localities, among others. Ultimately, the choice of synonym depends on the intended meaning and usage.