Covering 350 hectares, the Costanera Sur Ecological Reserve is the biggest and most biodiverse green space in the city of Buenos Aires. Despite its proximity to the busy downtown area, with the skyscrapers of Puerto Madero in plain sight, it's a remarkably tranquil oasis of calm, and a haven for wildlife.
Along several winding paths leading around three lagoons to the Rio de la Plata river, you can observe many different species of birds, mammals, reptiles and amphibians, as well as more than 500 species of native vegetation including meadows of pampas grass, forests of alder trees and many examples of the cockspur coral tree, Argentina's national flower.
The more than 2,000 species of flora and fauna that live in the reserve include lizards, turtles, coypus, and up to 340 species of birds that have been spotted. It is not uncommon to spot at least 50 different species of birds in just a two-hour visit.
The reserve is the unplanned result of an abandoned project to built a new adminstrative centre for the city by reclaiming land from the river. While the project was dropped, happily the city was left with a unique space that was taken over by nature. The area was declared a nature reserve in 1986 and in 2005 was declared a Ramsar area and was recognised as an Important Bird Area by BirdLife International owing to its importance as a major international wetland habitat for flora and fauna. It now forms part of the Río de la Plata Eco-route, a circuit of more than 100km that connects several green spaces such as the Paraná River Delta Biosphere, the Ciervo de los Pantanos National Park and the Pilar Municipal Natural Reserve.
You can walk around the park in about an hour, or hire a bike near the entrance.