Infrastructure is struggling to keep pace with population growth in the world's cities and more than a billion people now live in slums.

Forecasts predict that one in four people will be an urban squatter by 2030.

Al Jazeera's Gabriel Elizondo travelled to the Heliopolis shanty town in Sao Paulo as part of our Slum Cities series, where music is transforming the lives of children.

Source: Al Jazeera