Urban green areas create a healthy city where the natural environment and the built areas are interwoven. However, urban cities are facing stress between the high buildings with dense construction as a result of the rapid increase in urbanization, land value, and the decreasing of the proportion of green areas. Lacking green areas affects negatively on the development process in the environmental, social, and economic dimensions. The main aim of this study is to put an outline to increase the green area share in urban metropolitan cities as a holistic strategy for a healthier city. By Appling the concept of green roofs with top roof farming and green walls, it is possible to increase the green area share in metropolitan areas. In addition to enhancing the environmental problem, it can contribute to developing the urban food system and quality life. This study describes the significant role of urban green areas in cities based on sustainable aspects. The alternative ways of increasing the greenery in high-density urban cities are studied; some experiences in the world are described, and the situation in Cairo city is discussed.