São Paulo is a giant city with lots of nightlife, activities and art. What I liked most about this monstrous city (12 million in the city itself, 20 in the metropolitan area) is the number of parks and green areas it houses. Lungs needed to fight all the gases from cars.
Worthy of a visit: the beautiful Ibirapuera Park, with museums (like the Afro-Brazilian Museum) and events; the Metropolitan Cathedral in the center of the city; Paulista Avenue, a huge street with office skyscrapers on both sides; the art gallery; the Portuguese Language Museum; Praça da Luz; the Japanese neighbourhood.
I will always remember the first time I visited São Paulo, with that outdoor show in Ibirapuera Park. A jazz festival with artists from various countries that made us have a great time.