A 350-hectare nature reserve on the river bank east of Puerto Madero, created accidentally: the land was originally reclaimed from the Río de la Plata in the 1970s for a planned development that never happened, and nature moved in instead. Today it is the most biodiverse urban green space in Buenos Aires — over 300 bird species have been recorded, and the reserve provides habitat for foxes, coypus, armadillos, and over 50 species of amphibian.
The reserve is popular with joggers, cyclists, and birdwatchers at weekends; on weekday mornings it can feel surprisingly wild for a place 10 minutes' walk from the city centre. The lake inside the reserve attracts waterfowl year-round; the best birdwatching is at dawn and dusk. Free entry; bring binoculars.