Older inhabitants of Buenos Aires, or porteños, still recall when Costanera Sur was the site of a literal dumpster. Debris from across the city -- everything from demolitions to subway excavations -- was poured into the water, next to what once had been a glorious bathing site. The reclaimed land was meant to become the site of grand government facilities in the 1970s, but the project was abandoned without explanation.
Over the years, plants, birds, and other animals gradually took over the reclaimed lands, kicking off a virtuous cycle of regeneration. In 1986, the city government recognized the area's status as a sanctuary for wildlife and declared it an Ecological "Reserve" (to distinguish it from naturally-formed "Parks").
Still, the reserve mostly remained ignored by porteños, who tended to turn their backs on the polluted river. The area was further cut from the city by the then-derelict Puerto Madero, where crime thrived in the decaying docks between slowly corroding ships.
In the early 90s, another mega project, this time successful, was launched to restore Puerto Madero and repurpose it as a chic office-residential-restaurant area. Once the zone began to attract people back, the reserve was rediscovered by porteños, who enjoyed walking through the vestiges of the 1930s bathing facilities into a patch of wild nature, where the city's towers peek above the tall grass plants.
Today, the site is a magnet for porteños seeking to escape the city without traveling far. Stretched over 350 hectares, it is the city's biggest and most biodiverse green space. Visitors can try to spot more than 300 species of native and exotic birds, as well as over 500 species of native vegetation.
Several trails leading into the reserve provide for long walks into a surprisingly well-preserved area, its artificial nature only betrayed by the unusual nature of some of the rocks.