"Adjacent cities" refers to two or more cities that are located next to each other, usually sharing a border or being very close in proximity. Full definition
For that matter, some suburbs are actually quite urban, only separated from adjacent cities by arbitrary borders. (politics.stackexchange.com)
No reports of major implications have come out of this fire in the Beijing - adjacent city of Tianjin, but there is the perception factor. (pocketnow.com)
This Nashville - adjacent city also has a low crime rates, high graduation rates and high household incomes. (gobankingrates.com)