Parque Ecológico do Tietê is one of São Paulo's big breathing spaces, a vast riverside park on the east side of the city. The visitable section has lakes, trails, sports areas, and patches of preserved forest where you may spot monkeys, coatis, capybaras, and plenty of birds.
It is a good choice when you want a greener, less polished side of São Paulo. Bikes and paddle boats are usually the easiest way to cover more ground, and the small Museu do Tietê adds useful context on the river and its long struggle with pollution.