Alice Braga, actor

I was just 18 when I got the phone call from director Fernando Meirelles. I was still in high school and had only appeared in a few commercials. He told me he was looking for someone who wasn't famous, since he didn't want the slum kids who would be acting in his film, a crime drama set in one of Rio de Janeiro's favelas, to feel intimidated.

I didn't really audition: I just went to Rio and met the actors who had been chosen by the casting director, Fátima Toledo. About 2,000 young people had turned up after the studio placed an advert in a local paper. Of those, about 200 were selected for an "actors' workshop" lasting several months. Then they selected the leads.

Working with amateur actors was beautiful. They brought so much spontaneity to the film. They made it look real. We weren't allowed to read the script, though. Fátima wanted us to be emotionally and physically prepared, but never to memorise lines. Everybody improvised, including the professionals. That was a challenge, because it was the first time I had to actually build a character. The unknown is exciting but also terrifying.

This was only Meirelles's second feature film, so City of God was a turning point for him, too. He knew what he wanted, but he was never too pushy. We couldn't shoot at Cidade de Deus, the real City of God slum, though. It was too dangerous because it was in the middle of a drug war. Instead, we shot at Cidade Alta (Higher City), a similar-looking slum, using community members as security guards because they wouldn't let us bring our own. I don't remember feeling unsafe at any time. Sure, some of them were drug traffickers and what not, but nobody was carrying machine-guns.

It was a kind, tight-knit community. They were very respectful, generous and friendly. I think they were happy that we were telling their stories. Everybody welcomed me, even though I was from a different place and a different background. Some of them are still my friends.

My part in the film was pretty small, but my face was on the poster for the overseas release. That really got me noticed internationally. People wanted to know who that girl was. I was able to get an agent in the US, and my life changed completely.

Lamartine Ferreira, assistant director

Our goal with City of God was to do away with the prejudice that exists about favelas. Yes, there is crime in Rio, and we portrayed that, but we wanted to show that people from the slums can lead normal lives and improve their situation if they take advantage of their opportunities.

Rocket, one of the central characters, was born in the favela and has many things going against him, but he's able to realise his ambitions. He becomes a photographer and gets his pictures in the newspaper – and people come to understand that he is not just another criminal from the favela.

During the nine weeks of filming, we were in constant contact with the residents' association, and they helped us every step of the way. I would go to people's houses and meet the parents of people working in the movie. When a project is presented in a caring manner, you can enter and leave such communities: the drug traffickers were there doing their work, and we were there doing ours. We wanted to show what they do, but we did not want to be involved with them.

Some residents liked the result and others did not – but you can't please everyone. In the end, we only wanted to tell the truth about something that is very sad. Everyone was surprised and delighted when the movie was such a huge success. In the 12 years since it came out, many cast members have changed careers, but some are still acting. City of God left its mark on everyone who saw it. People still talk about it today.