Pope's message of hope as he visits Brazil's 'Gaza Strip'
They are some of the most dangerous, most crime-ridden places in the world, where even the police and army fear to tread.
But in one of the most highly symbolic events of his week-long trip to Brazil, Pope Francis ventured – on foot – into one of the country's notorious favelas, the slum-like shanty towns that sprawl around its big cities.
The 76-year-old shunned the bullet-proof popemobile normally used for such visits, instead walking around the Varginha favela, a poverty-stricken community in an area of Rio nicknamed the 'Gaza Strip' for its drug crime, violence and gang warfare.
He went there with a message to Brazil's poor and oppressed – not to give in or despair in their battle against the "evil" of corruption.
Brazil was beset by the biggest protests in a generation last month, with more than a million people taking to the streets to condemn government graft, poor public services and the cost of hosting the 2014 World Cup.
In an address from a platform overlooking a local football pitch, Francis alluded to that anger as he urged Brazilians not to yield to apathy.
"Here, as in the whole of Brazil, there are many young people. Dear young friends, you have a particular sensitivity towards injustice, but you are often disappointed by facts that speak of corruption on the part of people who put their own interests before the common good," the Pope said.
"To you and to all, I repeat: never yield to discouragement, do not lose trust, do not allow your hope to be extinguished."
In an apparent reference to the capacity of ordinary people to vote out corrupt governments and demand new leadership, he added: "Situations can change, people can change. Do not grow accustomed to evil, but defeat it."
The Pope was given a rock-star reception on his visit to Varginha, with people cheering him and offering up newborn babies for him to kiss and statuettes of the Virgin Mary to bless.
Once ridden with crime, Varginha was "pacified" last year when Brazilian police entered and cracked down on heavily armed drug gangs. Francis criticised that approach, which has picked up pace as Brazil tries to improve security ahead of next year's World Cup and the 2016 Olympics.
"No amount of 'pacification' will be able to last, nor will harmony and happiness be attained, in a society that ignores, pushes to the margins or excludes a part of itself," he said.
At the end of his tour of the favela, Francis delivered a blessing in the tiny chapel of Sao Jeronimo Emiliani, a plain building containing 18 wooden pews and with a white cross above the entrance.
He then visited a local family in their modest home, a small house with a lime green exterior and a single plastic chair on a narrow veranda.
Later, he traveled in a popemobile through a massive crowd in the pouring rain to a ceremony on Copacabana beach.
His arrival helped open World Youth Day and was his first official event with the hundreds of thousands of young people from from 175 nations who have flocked to a rain-soaked Rio for the Catholic festival. (© Daily Telegraph, London)