While there (about 10 years ago) we took a day trip to a national park on the outskirts of Rio.As our bus climbed the hill to get to the park (that area is very hilly) the guide directed our attention to a huge collection of broken down,ramshackle,structures on an adjacent hillside.She said it was a "favela" which,IIRC,is Portuguese for slum and that it was one of the worst in the country.She said it was so violent,so lawless,that the Brazilian *Army* didn't dare try to enter it even during *daylight* hours.
Brazil is a mess; very corrupt.