I am having trouble finding techniques that Nolan had used in the filming of this scene.
Here's a very technical explanation:
Returning to the Paris environment, Ariadne demonstrates her newfound ability to control the dream world by folding the streets in on themselves to form a giant "cube city."
The Dneg vfx team, lead by CG Supervisor Dan Neal, spent a week documenting the Paris location where main unit was scheduled to shoot. Lidar VFX Services scanned all of the buildings and then delivered highly detailed data from which Dneg built a series of Parisian apartment blocks. It wasn't possible to get above the buildings, so Dneg artist Lee Tibbets sourced photographs of typical Paris rooftops to fill in the missing areas.
CG Supervisor Philippe Leprince implemented the new ptex texture mapping techniques in Dneg's RenderMan shaders to allow the CG team to avoid the laborious UV coordinate mapping that is usually associated with models of this type. The final folded streets featured fully animated cars and people; anything that's not on the flat in the final images is CG.
The same quote can be found in this article, which contains additional information on the Paris scenes.