Making Rio's favelas safe: What you need to know
12 June 2012 Last updated at 14:00 BST
In two years' time the 2014 football World Cup Rio kicks off in Rio de Janeiro and security has become a top priority in Brazil.
A major army and police security operation has been launched to dismantle the power structure of Rio's armed drug gangs which control many of the city's slums, or favelas.
UPPs - or Pacifying Police Units - have been installed in 19 of Rio's favelas, and there are plans for more.
BBC Brasil's Julia Carneiro explains how Rio's favelas are changing.