城区 chéngqū urban district

Cheng District or Chengqu, a district of Shanwei City 汕尾市, Guangdong; city district; urban area

How to remember 城区: 城 town + 区 area = urban district.

Characters

城区 (chéngqū) means the urban/city district area, used in administrative and geographic descriptions.
Common in contrast pairs: 城区 (urban area) vs 郊区 (jiāoqū, suburbs) or 农村 (nóngcūn, countryside).
Very close in meaning to 市区 (shìqū, downtown/urban area of a city) - 市区 is the more everyday term, while 城区 leans slightly more formal/administrative, often part of a specific district name.
Used for describing where in a city something is: 位于城区 (wèiyú chéngqū, located in the city district).