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Watching draw bridges being raised over the Chicago River inspired the design of the folding street. All images courtesy of Warner Bros.

It all began with architecture. "Whether it's through the manipulation of structures to show the power of the dreamers, as in the folding streets of Paris, or in the crumbling towers of Limbo, which symbolize the advancing collapse of Cobb's mental state [played by Leonardo DiCaprio], the design of the built environment is always significant," explains Paul Franklin, the overall visual effects supervisor, who collaborated with Dneg's Pete Bebb, the CG supervisor, and Andy Lockley, the 2D supervisor, among others.

Production Designer Guy Dyas and his art department team gathered an extensive library of architectural reference, which the vfx team then built upon through post- production to develop a strong language of structure and style that drew heavily upon the history of modern architecture throughout the 20th century, especially for the climactic scenes in Limbo.

"In terms of the way that the dream worlds were depicted cinematically, the aim was to present everything with the conviction of total reality, as it was essential to the plot that the dreams appear real to the people experiencing them," Franklin continues. "The visual effects of Inception needed to integrate seamlessly with Wally Pfister's stunning cinematography which -- for the most part -- was hand-held in full daylight, giving it an immediacy that placed extraordinary demands on the vfx pipeline and the team at Double Negative.

"With the Paris sequences, Guy Dyas and his team had already produced some early concept images of how the folded streets would look when completed, but there was no indication of how we might go from normality to the 'cube city.' One of the great things about Inception was that it was the third time around for me on a Chris Nolan film, so I was able to draw on things that we had both experienced whilst working on the Batman films: We talked about watching the draw bridges over the Chicago River being raised, which include sidewalks and lamp posts as well as the road surface and how, from certain viewpoints, it looked as if the street itself were lifting up on a giant hinge. This then became the basis for the design of the folding street, hidden mechanisms suggesting a logical underpinning to Ariadne's dream world [played by Ellen Page]. Dneg CG Supervisor Ali Wortman created a previs animation of the folding street, which Chris then used to cue DiCaprio and Page as they stood on the Paris location -- Chris holding my laptop in his hands and directing the actors to look at the imaginary streets as they arced overhead."