Rio de Janeiro: Muggings, crowd violence, a terrorist attack -- there are a lot of potential problems to keep Olympics security chiefs in Rio de Janeiro awake at night a year before the 2016 Summer Games.
With more than 10,000 athletes and hundreds of thousands of fans to protect, Rio says it's taking no chances, deploying 85,000 security forces -- double the approximately 40,000 used at the 2012 London games.
Brazil is a violent country, with an estimated 52,000 murders a year, and Rio sees more than three of those murders every day.
However, Brazil has successfully hosted a string of mega-events in the last few years including the 2012 UN Rio+20 environmental summit attended by 191 countries, a visit by Pope Francis, the Confederations Cup and the 2014 World Cup.
"No other country has hosted so many events in such a short time. And this gave us great experience that we can apply to the Games," Rio's public safety chief, Andrei Passos Rodrigues, told a news conference.
These are the main four areas that security services are looking at: Although Rio crime stats have dipped, they remain extremely high, with an average of 3.4 murders daily in the first half of this year. Violence in Rio often grabs the local headlines, adding to a general atmosphere of fear.
Whole areas of the financial center are considered dangerous to walk at night, while most residents would currently refuse to go to the marina hosting the Olympic sailing contests except by taxi, because of the adjacent park's reputation for muggings.
Earlier this month even the metro, long a haven from street violence, saw a rare murder.
Still, by flooding the streets with some 47,500 security personnel, officials say they can guarantee a trouble free city during the two weeks of the Games. Brazil has such a low profile in world conflicts that the subject receives little attention in the national media or discussions of preparations for the Games. Still, the Olympics is inevitably seen as a major potential target for militant groups.
The 1972 massacre by Palestinians of Israeli athletes in Munich still looms over Olympic history, but today's potential threats -- including the feared use of amateur drones -- have greatly multiplied.
The country must "never lower its guard," Rodrigues said. Brazilian officials say they are working with counterparts from more than 90 countries to protect against militant attacks, and with Interpol to develop a strategy against cyberattacks.
Authorities have also been on fact-finding trips to big events in other countries, including the Tour de France and the Boston marathon, which was targeted by a bomb at the finish line in 2013.
"We have the same level of maturity in confronting terrorism as any other nation that proposes putting on events like this," Rodrigues said. The armed forces say they are ready to close airspace over Rio at any time and drones will be prohibited during the Games or over the Olympic Village.
Access to stadiums, X-ray machines and metal detectors will be controlled by unarmed soldiers and prison system employees. One thing they'll be on the lookout for is crowd violence, which has often been a problem at Brazilian domestic football (soccer) games.
In addition, several stadiums including the Maracana and the Deodoro are close to large slums, or favelas, further complicating the job for police. Rodrigues said a sign of success for his forces would be that nothing happens -- and "they are not remembered."
The run-up to the World Cup saw large street protests against the government's preparations for the tournament and against the world football governing body FIFA. So far, there is no sign of a repeat, with social media sites often used to coordinate protests going largely quiet.
Analysts say Brazilians were angry at the costs of the World Cup preparations but that although discontent remains high, the Olympics have not raised the same controversy. "Today people's problem isn't with the Olympics -- it's with the government," said Lamartine Pereira da Costa, an expert on the Olympics at the State University of Rio de Janeiro.