Places

cosmopolitan (environment)

metropolitan (city)

downtown

city centre

urban

the suburbs / suburban areas (NOTE: when referring to the suburbs, we generally always use THE)

rural

the outskirts

CBD (Central Business District)

city hall

coastal city

inland city

mountainous city

housing

accommodation

housing complex

industrial estate

housing estate

apartment (US) / flat (UK)

house

villa

2-storey house

5-level apartment building

office tower

skyscraper

landmark(s) buildings

marina

port / harbour

airport

bus/train/air terminal

urban sprawl

The people:

city-dwellers (this is the only word that focuses specifically on people who live in cities)

inhabitants

citizens

residents

commuters

internal migrants (people from the same country, but moving from another part of the country)

Population

overcrowded (too many people)

densely-populated (a lot of people in a given area)

sparsely-populated (very few people in a given area)

high-density housing (a lot of houses / apartments that are close together)