Buenos Aires , City (pop., 2010: city, 2,890,151; Greater Buenos Aires, 13,361,000), capital of Argentina. Located on the Río de la Plata estuary in east-central Argentina, about 150 mi (240 km) from the Atlantic Ocean, it is nevertheless a major port. First colonized by the Spanish in 1536, it was not permanently settled until 1580. It became the seat of the Viceroyalty of the Río de la Plata in 1776.
