Jacarezinho, Brazil

This favela is no paradise. With over 40,000 residents crammed into just 99 acres, Jacarezinho is the third-largest slum in Rio de Janeiro, a city notorious for its sprawling shantytowns. The area expanded rapidly during Rio's industrial boom, but today suffers from the typical ills of urban poverty - violence, drug dealing, and a persistent lack of government services. In 2021, at least 25 people were killed in a shootout with police, a grim reminder of the dangers lurking in these crowded streets. For anyone seeking a comfortable, stable life in Brazil, Jacarezinho is best avoided.