The study of the evolution of cities' entrances during time represents the social, cultural, political and economic changes, which had their implications on the settlement patterns. The spatial-physical structure of the entrances of today's cities and mega polis may be used as an evidence. The transformation of entrance spaces in old cities from defined gates, walls, and fortifications into entrance corridors, with speared residential complexes, industries, military uses, warehouses, junkyards, oil change shops, etc. in less than 100 years reflect the significant changes which are rooted in the uncontrolled growth of the cities. The undesirable environmental conditions of the entrance spaces of most cities and their adverse impacts on residents and new comers, on the one hand, and the role environmental design can play in the promotion of environmental quality, on the other, are the reasons why this study is taken up the protection and promotion of environmental and visual quality of cities' entrances as the research goal. In this study, first the entrances in traditional architecture and entrance spaces of old Iranian cities are investigated, as well as, the relationship between function and structure of city entrances and residents; desires and the capabilities of this space to meet the citizens' needs in the past. In the next phase, the characteristics of a few Iranian city entrances, considering the two criteria of, tourism and climate, are studied and the relationship between the city and the external spaces at enterances are analyzed. On the basis of these characteristics, and also some useful and renewable characteristics of entransces of old cities, patterns are developped to make link between the urban spaces with external environment. At eventually by using the findings of these studies and also by looking at the similar experiences in Iran and in the USA, design criteria and objectives are developed for the city enterances.