Rooftops are vastly underutilized spaces in the urban environment, yet it is possible for any landscape, plaza, or garden to be installed on a building or structure. In Europe, over the past thirty years, rooftops have become the focus of a quiet but steady revolution through the application of green roof technologies. It is significant that properly designed green roofs can emulate natural processes. Even the thinnest green roof can effectively absorb most rainfall events, reverse the urban heat island effect, and provide wildlife habitat. They also insulate buildings, extend the life of the roof membrane, increase property values, and vastly improve urban aesthetics. While Europeans have been enjoying these benefits for years, Americans are just beginning to embrace them. Green roof technology is so new to America, that there is far too little data published to guide landscape architects in the design process.