Increase in the population rate and the extent of urbanization in the last two centuries resulted in the concentration of the population around the growth poles. A large portion of this population lives in the peripheries of the large cities in informal settlements under inappropriate situations specifically in developing countries. Iran is one the countries that has severely experienced this problem since 1930s. Iranian cities are some of the biggest cities of Middle East to have been developed unequally, because of various factors including in-migration, unevenly distribution of resources, insufficient state policies and the local authorities haven't been successful on tackling the problem yet. The overconcentration of population in some major cities of the country is the result of centralization of main industrial and economic poles around these centers which leads to the immigration of unemployed people to these cities. Thus, this issue has a great impact on the unequal expansion of major cities. Tehran, as the largest and the most urbanized city of the country, absorb a large percentage of national resources and magnetizes many people with various socio- economic background. However, the polarized system of the city offers chances for those who can adjust themselves to the system, while the others that cannot afford living in the city boundaries, reside in the city fringes in substandard living conditions. Therefore, in Iran the inequalities between urban and rural, gradually has altered to inequalities within cities and the trend is more significant in some major cities including Tehran, Mashhad, Shiraz, Tabriz, Isfahan and many other cities. Furthermore, it is more challenging in the case of Tehran, when its population during 1920s and 1970s increased to thirteen times by the pace of rapid development, centralization and capital flow So, the city has expanded around its periphery specifically towards south and west. This process accelerated between 1970s and 2000s by implementing new legislation and master plans, and as a result, Tehran converted to Tehran Metropolis Region which is multicenter comprised of the central core which is the Tehran city, main access roads and other cores around which are the centers of residential and work concentration, reliant on the main city economically. This kind of urban sprawl is has accompanied with break in urban structure and fading urban sustainability as well as population movements and formation of spontaneous settlements which is the pressuring problem in cities of newly developing countries.