Reserva Ecológica Costanera Sur

The Costanera Sur Ecological Reserve is Buenos Aires' most improbable green space — 350 hectares of wetland, grassland, and forest on reclaimed land at the edge of Puerto Madero that is home to over 300 bird species and feels like a completely different ecosystem from the concrete city five minutes away. The reserve was created accidentally — land was reclaimed from the Río de la Plata in the 1970s and 80s for development that never happened, and nature took over the vacant lots with such enthusiasm that the city declared it a nature reserve in 1986.

The reserve's lagoons, reed beds, and scattered trees attract an extraordinary variety of birdlife — herons, cormorants, kingfishers, and the occasional Neotropical hawk — that makes it one of the best urban birdwatching sites in South America. The walking paths run for several kilometres through the reserve, and the experience of standing on the riverbank at the eastern edge, looking across the widest river in the world (the Río de la Plata is 200 kilometres across at its mouth) with nothing but water to the horizon, is a perspective on Buenos Aires' geography that the city's tree-lined streets never provide.

The reserve is free, open daily from sunrise to sunset, and is popular with joggers, cyclists, and the weekend crowds who come to barbecue at the river's edge. The sunsets over the city skyline — visible from the reserve's western paths — are among the best in Buenos Aires. The combination of free admission, genuine wilderness, and the surreal contrast with the skyscrapers of Puerto Madero a few hundred metres away makes this one of the city's most rewarding and undervisited attractions.