Buenos Aires

34.6037°S, 58.3816°W.

Second-largest metropolitan area in South America, founded by Spanish navigator Pedro de Mendoza in 1536 on the south bank of the Rio de la Plata estuary. The original settlement was abandoned within five years; the permanent founding by Juan de Garay dates to 1580. The city's grid plan radiates from the Plaza de Mayo, where the Cabildo (1610), Cathedral (1791), and Casa Rosada (presidential palace, 1898) form the foundational triangle of Argentine state authority. The Avenida 9 de Julio, completed 1937, is one of the widest urban avenues in the world at 140 metres across with sixteen lanes. The Obelisco at its central intersection stands 67.5 metres tall, erected in 1936 to mark the 400th anniversary of the city's first founding. The Rio de la Plata at this point is 220 km wide — the widest river mouth on Earth.

The city sits at the edge of an estuary so wide it cannot be seen across.