With 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, which lead to the Rio de la Plata river, and around three lagoons, you can observe different species of birds, mammals, reptiles and amphibians, as well as more than 500 species of native vegetation including meadows of pampas grass and forests of alder trees.
It's also a great place to unwind, and is one of the city's favourite spots for walking, running, cycling and family picnics.
The reserve grew out of a project to expand the city by reclaiming land from the river, and while the project was dropped, happily the city was left with a unique space that was taken over by nature. In 1986, the area was declared a Natural Park and Reserve. The reserve has since been recognised by BirdLife International and the Ramsar convention as an Important Bird Area because of the more than 300 species of native and exotic birds than have been spotted.
You can walk around the park in about an hour, or hire a bike (bikes are available for hire at the main entrance at Av. Tristán A Rodríguez 1550 in Puerto Madero.
The reserve is open every day except Monday. Entrance is free and tours, also free, run on weekends and public holidays at 9.30am and 4.30pm. There are also tours at night on the Friday closest to a full moon. More information can be found on the Facebook page.
For an English-language tour, email or call ahead to reserve (email@example.com; +54 11 4893 1853 / 4313 4275).
Read more about birdwatching in Buenos Aires.