The Ecological Reserve is an unusual and unexpected consequence of highway construction throughout Buenos Aires during the mid-20th century. Construction debris and the rubble of demolished buildings were unceremoniously dumped into the Río de la Plata. Over time, sand and sediment began to build up, and then grass and trees began to grow. The birds followed, and now the area is a preserve. Various companies offer biking and bird-watching tours of the area. Ask your travel agent about it or see our list of tour companies. Since there are few genuine beaches in the Buenos Aires area, some people come here to sunbathe, sometimes in the nude. Whatever you do, don't go into the water, since it is heavily polluted and still full of rough construction debris in some parts. The Costanera walkway, extending from Puerto Madero, has been improved since 2007, with ice-cream kiosks and other services for the increasing amount of spillover wanderers from the port. In spite of its being a preserve, development is slowly encroaching as the Puerto Madero area grows. Though the police do have a patrol station here, some homeless people also camp out here, meaning you should be cautious.