The city centre lies in the area originally defined by the old ramparts, which are still referred to as the Fortification Ring (''Fæstningsringen'') and kept as a partial green band around it. Then come the late-19th- and early-20th-century residential neighbourhoods of Østerbro, Nørrebro, Vesterbro and Amagerbro. The outlying areas of Kongens Enghave, Valby, Vigerslev, Vanløse, Brønshøj, Utterslev and Sundby followed from 1920 to 1960. They consist mainly of residential housing and apartments often enhanced with parks and greenery.