Costanera Sur Ecological Reserve
An accidental wetland on reclaimed rubble beside the Buenos Aires skyline, now 350 hectares of lagoons, grassland and 300 bird species.
Updated 18 October 2026

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The Reserva Ecológica Costanera Sur exists by accident. In the 1970s a plan to extend the city into the river filled a stretch of the Plata with rubble from demolished buildings, then abandoned the project; water pooled behind the embankments, seeds arrived on the wind and in birds, and within a decade a wetland had formed on the ruins. Today it covers around 350 hectares of lagoons, reed beds, pampas grassland and willow woodland immediately beside the towers of Puerto Madero, with more than three hundred bird species recorded, along with coypu, lizards and the occasional river turtle. Wide gravel paths cross it, cyclists and joggers use it heavily at weekends, and viewpoints look out over the brown expanse of the Río de la Plata.
History
The Municipal Riverside resort opened in 1918, and in summer thousands of porteños came on foot, by car or by tram to bathe in the river, men and women kept apart by a long pier under rules of 1923; in the 1920s and 1930s bars and cafés with music and shows lined a promenade with Lola Mora's Nereids Fountain and a monument to the Plus Ultra airmen. Decline began at the end of the 1950s, as buildings decayed and bathing was banned because of pollution, and in 1978 work began to reclaim land in front of the old resort, building embankments of rubble from demolitions for urban motorways and draining the water inside, though the work was never finished (Wikipedia, Costanera Sur Ecological Reserve).
Highlights
- The lagoons - open water and reed beds with herons, ducks and coots.
- The city contrast - Puerto Madero towers rising directly behind the wetland.
- The river shore - views over the Río de la Plata from the outer path.
- The wildlife - coypu, lizards and hundreds of bird species.
When to go
Year-round; spring and autumn bring migrants and comfortable temperatures. It closes on Mondays and after heavy rain when paths flood. Early morning is best for birds and cooler air, as there is little shade.
Good to know
Paths are wide gravel tracks shared with cyclists and runners, so it is a city park with wildlife rather than wilderness. Summer heat and mosquitoes are significant. The river itself is muddy brown and not for swimming.
Nearby
Puerto Madero and its docks adjoin the reserve; San Telmo lies a short walk west.
Key facts
Source: Wikidata, item Q1034280, read on 18 October 2026.
What to pack for Costanera Sur Ecological Reserve
Chosen from what this place is for. Tap a kit for the full checklist.
- Broken-in walking shoes or boots - Grip and ankle support matter more than looks; never hike in brand-new boots. Find on Amazon
- Reef-safe sunscreen - High SPF that will not bleach the coral you are swimming over. Find on Amazon
- Padded shorts - The one thing that makes a full day in the saddle bearable. Find on Amazon
- Binoculars - The single best wildlife tool - even a compact pair transforms a sighting. Find on Amazon
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