To be clear, we're not talking about Central City, Missouri - the urban center that would act as the backdrop for Barry's police career, previously rumored to be 'more Se7en than superhero.' To explain Barry's powers means explaining their source: in short, an alternate dimension of the universe dubbed 'the Speed Force.'
Over the years, the Speed Force has been described as an imperceptible '4th dimension' (think dark energy), or even a fully-realized world that only speedsters can travel to. Since audiences will need to get on board with Barry's powers for the film to work - and need some serious spectacle to qualify the film as a blockbuster - picking a well-developed and scientifically sound interpretation of the Speed Force will be key.
If the Flash movie can tackle that world and be a moody crime thriller all at the same time, it could walk the line between both Man of Steel and The Dark Knight.