are in the northeastern portion of the administrative division and are part of the Guangdong-Hong Kong-Macau Greater Bay Area, the biggest built-up area in the world with more than 65,565,622 inhabitants as of the 2020 census, encompassing Shenzhen, Dongguan, Foshan, Zhongshan, Macau, the main part of Guangzhou, and small parts of Jiangmen and Huizhou cities but with Hong Kong not quite conurbated yet.

According to a report released in 2014 by the Chinese Academy of Social Sciences,