Modernization of the country has led to a transformational shift in the structure of Tehran in different courses of time that was based on the expansion of commercial streets and centers. Starting from Grand Bazaar as the traditional center for mercantile activities and also the center for cultural, religious and communal exchanges; this transformation was formed by creation of new commercial zones within three different periods:
  1. First Pahlavi (1925- 1941): in this period commercial extension grew detached from Grand Bazaar while the inner structure of Bazaar continued developing. Thus dissemination of commercial extensions appeared.
  2. Second Pahlavi (1941- 1979): in this period evolution of commercial functions occurred in three main phases, which continued after the revolution of 1979. In the first phase by the beginning of transformation of Grand Bazaar and its appearance partially changes following the conjunction of production sectors and older extensions. In the second phase Pahlavi Street starts acting as the backbone for commercial and bureaucratic distributions. This development moved through Pahlavi Street towards north, passed Valiahd (current Valiasr) Square and continued to Vanak and Tajrish Squares. In the third phase, after 1979, following the urban growth and the urge for creating new commercial hubs, the pattern of growth for commercial functions became denser in a greater scale.
  3. Post- revolution (1979 – present): in this period commercial functions expanded in Tehran regarding the major urban structure and inside the boundaries of this structure based on means of accessibility and distribution of users’ population; and both circumstances are almost the same as the previous era (Pourjafar et al, 2014).
Generally, there has always been a tendency to move towards north because of the geographical setting of Tehran. Such growth has been constant up to present day; and although a partial reason has been to access clean water and fresh air, in the 1960s this spatial south-north axis took a sociological dimension and impacted the politics of the country’s class struggle. South of Tehran, including the cemetery of Rey, continuing towards Grand Bazaar and poor Qajar residential districts was in contrast with the wealthy north, which included modern villas and mini markets, enjoying fresh air and clean water. Although this vertical axis was initiated due to historic and geographic needs, the following spatial segregation was embodied in this northward urban expansion during the last two decades pre- revolution (Adams, 1973). As Griggor (2016) mentioned, by the moving of the ruling monarch to the northernmost of Tehran, in 1959, historical urban development was empowered socially and symbolically. Thus, they intensified the impact of this south-north axis of social promotion.