For the past four years, Dutch artists Jeroen Koolhaas and Dre Urhahn have been splashing paint on Rio de Janeiro's favelas, transforming the hillside slums into clustered monuments of urban art.

The neighborhoods aren't just changing aesthetically. "About one-third of Rio de Janeiro's population lives in favelas," reports mental_floss. "To prevent kids from getting caught up in the drug trade, the Favela Painting project pays Brazil's youth to create murals for their communities. As a result, armies of teenage artists are giving their neighborhoods new faces—ones covered in bright, cheerful colors. The hope is that within the next few years, the entire landscape of favelas will become a massive work of art, drawing attention to the needs of the poor and filling the community with pride."