According to a United Nations forecast seventy percent of the world population will be living in cities by 2050 ( UNFPA 2007 ). Such a major shift away from rural and naturally vegetated areas to the polluted, noisy, and crowded concrete jungle of modern cities is and will continue to be profound. We must find new and innovative ways to better integrate nature into our ever expanding cities. Green roofs and parks are one way to do this but there are substantial amounts of vertical space that for the most part have been underutilized. Green walls not only bring nature back into city life, they do so in a way that is accessible to everyone. Currently green walls are at the cutting edge of interior and architectural design trends but they are also being integrated into sustainable building design for their numerous environmental benefits. This article aims to clarify what green walls are, going into detail about the various technologies available; the pros and cons of each; and the ecological, social, and economic benefits of these living works of art.