In these unlikely locations, Fernando Meirelles, the director of City of God, and his producer, Simon Channing-Williams, set up cameras, lights and cables to film the thriller about love, betrayal and murder that premieres today at the London Film Festival.
"Within 24 hours of arriving in Kenya on a scouting trip, we knew we had to film here, even though we were warned that no one would insure us, and that big movies were only ever shot in South Africa," said Channing-Williams.
"Edward Clay, the British ambassador to Kenya, introduced us to various government ministers, who then got us letters of safe passage that helped persuade insurers that we should film here."
In the end, the seven weeks of shooting in the summer of 2004 changed the lives of everyone involved. The Hollywood stars felt they had seen something extraordinary. By the time the filming wrapped up, the cast and crew were determined to help the local people where they could and promised £75,000 of their own money to set up the Constant Gardener Trust.
Weisz, who had only ever visited Africa as a tourist before, told reporters: "I had never seen poverty like that. It was extreme and tragic, and I felt a wave of guilt being a wealthy, white Westerner walking through those slums filming a movie.
"On the other hand, I was struck by the spirit of the children, who clamoured around us and welcomed us," she added.
Channing-Williams was given such a warm welcome by the Turkana, Samburu and other tribes in northern Kenya that he was made a tribal elder, complete with ceremonial robes and "the right to take a 12-year-old wife, if I should want to".
And the local children were equally awestruck. Elphas Omollo, a pupil at the Kibera school where some of the filming took place, still remembers it all vividly.
"I saw these long, long cables and big cameras," he said. "They told us they were making a film but I don't know what it was. But I think now I would like to be an engineer and learn to use those machines."
The opening scene of the The Constant Gardener is in Loiyangalani, the wild deserts of northern Kenya, where Tessa Quayle (Weisz), the wife of a British diplomat, is murdered just as she was on the verge of uncovering a conspiracy involving the testing of a new drug.
Her husband, Justin Quayle (Fiennes), continues her investigations in Loiyangalani and Nairobi, determined to expose how pharmaceutical companies use African people to test drugs that are destined to become huge money-spinners in the West.
It is easy to see why the director of photography, César Charlone, was keen to film in Kenya to convey the beauty, drama and terror of the storyline.
The scenery in Loiyangalani area is dramatic - bright, unfaltering light and empty landscapes where Turkana tribesmen herd their cattle, carrying only wooden stools to sit on and Kalashnikov rifles to defend themselves with.
Kibera, the location for another large section of the film, is the largest slum in Africa, where one million people live crushed inside tin shacks and rotting wooden cabins. A single frame shot in Kibera would give an instant impression of the country's poverty.
In Loiyangalani, the local Turkana tribesmen had told the cast and crew that they desperately needed a high school.
They had access to primary education they said, but no one in the community had attended a secondary school because the nearest one was too far away for them to get to.
In Kibera, the requests were less ambitious. The crew built water tanks so families had access to clean water, a bridge so the locals would not have to wade through a filthy stream to get to a health clinic and a new classroom at a local nursery school.
"We asked people in both communities what would be of benefit to them most, and we built exactly what they asked," Channing-Williams said. "It's a small thank you for the huge welcome they gave us. Who knows, we may even get some money from the big drug companies to build some health clinics too."Reuse content