Rio de Janeiro, Brazil, favelas
In the early 1900s, migrants began flooding Rio looking for work. Unable to afford proper housing, they began constructing their own slapdash neighborhoods, ones that didn’t adhere to building codes or have any sanitation.
Today, there are an estimated 1,000 favelas in Rio that house 1.5 million residents. The favelas are so dense that, in many cases, roads and utilities are impossible to install and crime runs rampant.