Article: Of much greater importance is the division of the city into 62 barrios: neighbourhoods or wards. Many of the city's barrios—such as Sayago, Ituzaingó and Pocitos—were previously geographically separate settlements, later absorbed by the growth of the city. Others grew up around certain industrial sites, including the salt-curing works of Villa del Cerro and the tanneries in Nuevo París. Each barrio has its own identity, geographic location and socio-cultural activities. A neighbourhood of great significance is Ciudad Vieja, that was surrounded by a protective wall until 1829. This area contains most important buildings of the colonial era and early decades of independence.

Question: What had many of the city's barrios previously been?
geographically separate settlements