And from portugal, we head to rio, in brazil. Tonight, the iconic statue, looking down on the great city. As police are taking drastic action. Millions of visitors will soon flock to rio for the world... See More
And from portugal, we head to rio, in brazil. Tonight, the iconic statue, looking down on the great city. As police are taking drastic action. Millions of visitors will soon flock to rio for the world cup and then the olympics. So, what will that country do about the dangerous circle of hell swarming the hills? "Nightline" anchor dan harris has this report tonight. Reporter: Good evening, the very word of ryo conjures images of sun and sand. But with the world cup and the olympics fast approaching, police are scrambling to clean up rio's vast criminal underworld. This is a war for paradise and we went to the front lines. Just minutes from iconic beaches with names like copacabana and ipanema, there are massive shanty towns called "favelas," most of which are effectively ruled by violent drug gangs. This is an open air market, this is his best seller, this is $5 american of cocaine, his best seller. Complete with piles of color coded drugs. I mean, it blows the mind to be in this place where everybody's selling drugs. No police. Nobody's batting an eye. It's just business as usual. And this -- just keeps going and going. Is what's known as a crackland. It's amazing. There's just no fear of the police. Just smoking right out in public. In another crackland, this one, the length of an entire city block -- they've got kids here. We found this 16-year-old crack addict. We wanted to go to the source of this misery, the drug kingpins. In a tiny room down a back alley, we scored a very rare interview with a drug lord, draged in gold and carrying a semiautomatic rifle. He demanded we conceal his identity. Given how serious the crack epidemic is here, do you worry at all about selling that to the community? Then, he surprised us with a question of his own. I took a moment to absorb this comment, and then the drug lord started chuckling. Fair point. Fair point. Now, as rio prepares to host millions of sports fans, police have launched a war to uproot the gangs. But this urban counter-insurgency campaign is massively controversial, because rio's police have a long history of brutality and corruption. Just look at this video of a police helicopter firing wildly in the middle of a neighborhood while in pursuit of a drug lord. It's extraordinary video and the police defend their tough tactics, but we met many people in rio who said, point blank, they would rather live under the gangs than the police. They have harrowing stories and videotape of policebrutality. Much more on that tonight on "nightline," diane. All right, thank you, dan, for being here and it is great to see you at the new anchor of "nightline." Reporter: Thank you. And you can see his entire report, as dan said, on "nightline." That will be tonight.
This transcript has been automatically generated and may not be 100% accurate.