Tattooed onto the concrete skin of the city, graffiti plays an ambivalent role in the aesthetic of the urban spaces. While the sprayed, drawn or painted markings often rise to the status of art form, adding life and color to dull gray surfaces, they can also make a street corner into a darker, less humane space. The difference may lie in the intentions of the creator. When graffiti is an act spontaneous self-expression or communication, their effect is to transform a generic structures into unique and meaningful landmarks. When graffiti is intended ...