There are cities, then there are large cities, and then there are really large cities. With a population around 18 million, Sao Paulo is certainly the latter: Not only is it the largest megalopolis in South America, it's also the third largest city in the world. Investment from foreign companies (especially American automakers) pushed the city's economy into the stratosphere over half a century ago, and it's showing no signs of stopping. Luckily, sheer size alone is not what defines Sao Paulo. Its cosmopolitan residents pride themselves on living a stylish, urbane lifestyle. The restaurants here are world-class, the art and music scene are top-notch, the nightlife unstoppable, and the shopping second to none. The pace here is faster, and in many ways, one could say Sao Paulo is the New York to Rio de Janeiro's Los Angeles.
Years of growth have brought immigrants to Sao Paulo from all over, resulting in a city that's not only the most diverse in the country, but one of the most multicultural in the world (it's home to the largest Japanese population outside of Japan). Growth hasn't always been evenly achieved, though: Sao Paulo is one of the richest cities in the southern hemisphere but also has intense income inequality. Like in many booming metropolises, infrastructure has not been upgraded to cope with the inflating population, resulting in urban sprawl and some of the most horrific traffic conditions in the world.
Sao Paulo still provides a unique urbane experience, even for self-proclaimed cosmopolitans. And as in many cities that work hard, it's expected for residents to play hard, too.
The key to enjoying your time in Sao Paulo will rely heavily on avoiding its legendarily awful traffic. Most points of interest for visitors will be in Centro, Jardins, or Higienopolis, so choosing to stay in those neighborhoods will minimize commuting on the city's clogged, overburdened roads. To get off the beaten path, Itaim Bibi is a residential area that still boasts great shopping and hotels.