Urban planning is the concept that defines a technical and political process concerned with the development and use of land,protection and use of the urban environment, in order to better accommodate the growing population of the urban and suburban areas of any city. It is is a concept in which the social, environmental and economic aspects of sustainability all merge together.Although we tend to think of it as a new development,urban planning is not a new concept. Since antiquity there are texts and designs of cities built in order to make them livable and safe for the population. One of the main elements in urban planning and urban design is green open space. However, as the human society is growing up, this development is bringing some problems to our earth since there is over exploitation of the world resources,resulting in more pollution and loss of biodiversity. We know that green open spaces have always been beneficial to human kind,not only because they keep guard of global warming,which if left uncared for has destructive results for our world, but also because they act as a source of food for us,in both a direct and indirect manner. Open spaces,be it natural or manmade,contribute to the quality of life in many ways. Beside important environmental benefits (such as improvement of the quality of air, soil and water, decrease of noise levels, reduction ofhigh temperatures), these areas provide social psychological services which are critical for the livability of the city and well being of urbanites.It is true that if you build a bigger city you will consume more sources and also you could have big impact to the environment, and if you are not limiting the growth of your cities you will lose a lot of nature area. However, big cities have a lot of advantages and opportunities thus we cannot do away from them because of green open space. Big cities are good for economy so to have big cities is not a problem. It depends upon how you plan for them. You have to limit the growth of the cities, integrate cities with environment and make sure that people have more contact with the environment. And as you know, you cannot achieve this without good planning. Green open spaces add up to the economy of a city: they promote the image of the city, increase the selling point. They contribute ecologically because they diminish the process of erosion and promote biodiversity.These above functions can be combined with each other. For example, the functions of green open space are water conservation and recreation. Furthermore, green space has multifunctional purposes like encouraging cycling and enhancing community health.As it is stated above, today, green open spaces are mainly planned with a purpose of fighting against global warming, this is why is important to talk about its role in combating against this worldwide issue. In conclusion, due to the functions and the role green open spaces play in the cities, they are fundamental elements, inductors of quality of life. When they get organized in systems like the green structure, their value is potentiated and incremented then contributing more efficiently to the quality of life. It is for that reason that green open spaces have to be promoted in the whole world.