No. 6 Rio de Janeiro
For years now, the Brazilian city of Rio de Janeiro has made just about every short list for the world's most violent and dangerous cities. Plagued by violent gun crime, assassinations and drug-trafficking, nearly 50,000 people have died of crime-related violence in Rio between 1978 and 2000. The city's crime problem was put on display once again this year for the entire world to see during the annual Carnaval celebration in Rio. Despite the deployment of nearly 10,000 police officers, the festivities were still marred by unusally high instances of robbery, assault and violence. Crime has been an embarrassment for Rio, placing the city's bid to host the 2016 Summer Olympics in jeopardy.