I live in São Paulo, biggest city in Brazil. It has a 20.000.000 population on it's metropolitan area. It's a place of extremes, I guess. It's the most developed area in the country, but has a hell lot of inequality, with some very wealthy neighbourhoods side by side with very poor and violent regions, with lots of intolerance between different classes. The city expansion was chaotic, with very little urban planning, so everything is a bit chaotic and not much pretty. It's kinda ugly to be honest, with a very poluted river crossing it. Everything is overpriced and the living cost is way above the average... you can buy bigger property in New York for a lower price than here.
Transit is one of the worst in the world, with only 5 subway lines and traffic congestions everywhere. My commute is only 6 miles, but in the worst days, it take about 1 hour and half to get home. Sometimes it's faster to go from my parents house to my work than going from my house to work. They live in a city 60 miles from São Paulo, by the way. It's that bad.
For all the terrible things, though, it's a cultural cauldron. Lots of immigrants, mostly italians, spanish, germans, chinese and japanese. People from all over Brazil come to São Paulo to try a better life, bringing their culture with them. Like US, Brazil is a gigantic country and each region is completly unique in terms of culture... so São Paulo have a bit of it all. It's hard to think of something that you can't find here.
There's major brazilian museums here, like MASP, Pinacoteca, SP Museum of Modern Art, Latin America Memorial. There's a beautiful park called Ibirapuera. The Interlagos circuit is where the brazilian F1 Gran Prix is held . The city center is very antique, with beautiful historic buildings and lots of different bars to hang out. It's not uncommon to visit a bar and find out that the owner don't even speak portuguese. There's a neighbourhood called Liberdade (Liberty, in portuguese) that's populated mostly by chinese and japanese people and it's a must go place to eat delicious food for a reasonable price.
The people born here have a fame of beign overstressed, always busy and not much easy going... so, pretty much the contrary of the brazilian stereotype. Others states consider the "paulistas" very snotty people, and it's kinda true. São Paulo thinks itself as the most import thing in Latin America. But it's a stereotype... the city has every kind of people and you can find very friendly folks around here.
To finish, a beautiful music about São Paulo, by a famous brazilian singer, Caetano Veloso:
http://www.youtube.com/watch?v=4V9Z9aBYt4g
Translation to the lyrics:
http://lyricstranslate.com/pt-br/sampa-sampa-its-nickname-city-sao-paulobr.html