So Paulo, or Sampa as it is also often called, is the largest city in Brazil, with a municipality population of 12.1 million, and about 21.3 million in its metropolitan region - the most populous of the Americas and the Southern Hemisphere.
The region of modern-day So Paulo, then known as Piratininga plains around the Tiet River, was inhabited by the Tupi people, such as the Tupiniquim, Guaians, and Guarani. Other tribes also lived in areas that today form the metropolitan region.