This is a 150-foot Dark Knight Rises ad painted on the side of a building at 315 Park Avenue South in New York City.
The process:
A life-sized rendition of the artwork is broken down into a simple outline. This is called the cartoon and is, in fact, where the modern use of the word “cartoon” comes from.
Holes are punched through the outline to form a dotted stencil that is then gone over with a charcoal pounce. By the end, they have the wall mapped out with the most basic shapes and proportions in place The oil-based paint is then mixed to match the larger portions of the painting, leaving the subtle blending and mixing to be handled ala prima on the wall.
Each painter has a print-out of the design strapped to their arm, like a mini shield, that they use as a guide as they flesh out all the details.
It took four guys about five days of sunrise-to-sunset painting to complete The Dark Knight Rises.
Source: [Geekologie]