The Reserva Ecológica is a strange but wonderful place, a fragment of wild and watery grassland stretching for 2km alongside the Costanera. Having self-seeded with grassland after the landfill project was abandoned in 1984, the reserve offers a juxtaposition of urban and natural scenes, whether factory chimneys glimpsed through fronds of pampas or the city skyline over a lake populated by ducks and herons. Inside the reserve, near the entrance, the visitors’ centre displays panels explaining the park’s development and serves as the starting point for ranger-guided walks along the park’s many trails (Sat & Sun 10.30am & 3.30pm). Full-moon nocturnal tours (weather permitting) allow you to spot all manner of creatures, mainly birds, which keep a low daytime profile. There is a surprising diversity of flora and fauna in the park, with over two hundred species of bird visiting during the year. Aquatic species include ducks, herons, elegant black-necked swans, skittish coots, the common gallinule and the snail hawk, a bird of prey that uses its hooked beak to pluck freshwater snails out of their shells. The park is also home to small mammals, such as the easily spotted coypu, an aquatic rodent, and reptiles such as monitor lizards. The reserve’s vegetation includes the bright red ceibo, but the most dominant plant is the cortadera, or pampas grass.