Pope Francis ventures on foot into Rio slums
They are some of the most dangerous, most crime-ridden places in the world, where even the police and army fear to tread.
But on Thursday, in one of the most 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.
Latin America's first Pope was later confronted with starkly contrasting images of life in Rio de Janeiro when he presided over a huge gathering on glamorous Copacabana beach, where he addressed the hundreds of thousands of Catholic youth who have converged on Rio for the biennial World Youth Day, braving cold rain and winds.
He described the gathering on the beach as "an immense feast of faith" and said the young people had been welcomed by Christ the Redeemer, the giant statue that looms over Rio.
"I always heard that the Cariocas (Rio residents) didn't like cold and rain. Your faith is stronger than cold and rain. Congratulations," the Pope said, after being treated to religious choirs, samba songs and dance routines.
Earlier, the 76-year-old shunned the bullet-proof Pope-mobile normally used for pontifical 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 hit by the biggest protests in a generation last month, with more than a million people taking to the streets of the country to condemn government graft, lagging public services and the cost of hosting the 2014 World Cup.
In an address from a platform overlooking a local football pitch yesterday, the Argentinean Pontiff 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 new-born 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 in preparation for next year's soccer World Cup and the 2016 Summer 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.
While Brazil has enjoyed an economic boom in recent years, development is patchy and the gap between the very rich and very poor has widened.
The Pope, who took his name from St Francis of Assisi and has called for a "poor Church for the poor", appealed for greater concern for those on the margins of society, echoing messages he has delivered in Rome since being elected pontiff in March.
He called on "those in possession of greater resources (and) to public authorities" to work for "a more just world, marked by greater solidarity".
As he was cheered by inhabitants of the favela, where poverty, unemployment and substance abuse are daily realities, he said: "No one can remain insensitive to the inequalities that persist in the world." He condemned what he called "the culture of selfishness and individualism that often prevails in our society." Francis walked around the favela under a giant white umbrella, his nose bright red from the cold and rain that has marked his time in Brazil since his arrival on Monday.
Local people wore woolly hats and plastic rain capes to ward off the heavy rain.
Francis was given an ecstatic welcome, with people cheering and reaching over metal barriers in an attempt to shake his hand.
The crowd of smiling black, brown and white faces represented the full spectrum of multi-racial Brazil.
He clasped hands with children and was given as a gift a scarf representing San Lorenzo, the Argentinean soccer club he supports.
He 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 looking out onto a potholed, rain-slick road. Outside the little house hung yellow and white balloons – the colours of the Vatican City State