Twin cities

two cities or urban centres that are founded in close geographic proximity and then grow into each other over time

The term "twin city" (or "twin town") refers to a city or town that is very close to another city or town that together form one urban area but are still different to each other.

In Australia, the term is used to refer to cities or towns that are close to each other but are on other sides of a state border or a river. Some examples include the Gold Coast-Tweed Heads area (the Gold Coast is in Queensland while Tweed Heads is in New South Wales) and the Albury-Wodonga area (Albury is in New South Wales while Wodonga is in Victoria; these cities are also separated by the Murray River).