The Vali-Asr, formerly known as the Mossadegh, and before that, Pahlevi Street, is one of Tehran’s main thoroughfares. Twenty kilometers in length, it is the world’s longest inner-city road. Flanked by sycamore trees, it runs from the low-lying south up into the northern part of the Iranian capital and on to the foothills of the Alborz Mountains. Lining this incline of some 800 meters are countless stores, restaurants, and parks, together with key government and cultural institutions. To follow the Vali-Asr is to trace Tehran’s urban development since the nineteenth century and get a sense of the extreme north-south social divide which still characterizes this metropolis today. Within this region’s hot and dry climate, the higher plains, with their cooler summers and frequent rainfall, offer far more comfortable living conditions, which may explain why the north was claimed by the city’s more prosperous citizens. It was here that the first modern residential district for the upper classes was built, leaving the poorer people to settle in the south, directly abutting the central Iranian steppes, and contend with a far less hospitable climate. Due to the massive rural exodus in the second half of the twentieth century, illegal settlements sprung up on these wastelands, which are also home to Iran’s largest industrial zones.

In 1785 Tehran became the capital city of the Persian Empire. Within just half a century, the population rose from 15,000 to 250,000. From the twentieth century onwards, Western architectural styles were in the ascendency and the city slowly lost its traditional face: the secluded and private courtyards hidden away behind high walls gave way increasingly to tall buildings and tower blocks facing outwards; initially under Shah Reza Pahlavi, who since the 1930s had been pursuing a Haussmannian planning policy and developed the north of Tehran into a second city center; and subsequently under Mohammad Reza, who seized power after the overthrow of Prime Minister Mossadegh in 1953, and who endeavored to accelerate the pro-Western course embarked upon by his father, with the backing of the United States. From 1963 onwards, the Shah implemented a modernization program which went down in history as the “White Revolution.” At the time, Tehran boasted some 2.5 million inhabitants and was a popular migration metropolis. Persians, Turks, Kurds, Arabs, Balochs, Lurs, etc. lived together peacefully here with other religious minorities such as the Zoroastrians, Jews, and Armenian and Assyrian Christians, albeit in separate districts.

Thanks to the enormous rise in state revenues from the export of crude oil, urban development proceeded apace. The vast settlement Shahrak-e Ekbatan, a modern mega-structure in the western part of Tehran’s expansion zone, containing some 15,500 dwellings and over 70,000 residents, is a shining example of the optimism of the 1970s. Some claim that it was in Ekbatan that the Iranians as a nation finally embraced urbanization. However, the reforms of the Shah era benefited only the select few. The previously dispossessed landowners now received stakes in the rapidly growing industrial sector. Farmers had to raise loans to work their fields and provide for their own irrigation, livestock, and machinery themselves, which their income from agriculture was insufficient to cover. Thus the poorer and richer sections of society became ever more polarized.

During the Iranian Revolution of 1978/’79, it was above all the upwardly mobile, urban middle classes, students, public servants, merchants, business people, and industrial workers who joined the mass protests against the autocracy of the Shah and their exclusion from the political decision-making processes. The Shah fled into exile. The key integration figure and revolutionary leader was Ayatollah Khomeini, who aspired to establishing an Islamic Republic. In a referendum held in March 1979, his proposal was approved by ninety-eight percent of Iranians, although no other alternatives were on offer. The Islamic Republic was officially proclaimed and followed by the Islamization of all public offices and institutions: the judiciary, schools, and universities. Women were henceforth ordered to adopt the Islamic dress code, and large sections of industry were nationalized. Critics were threatened and persecuted. Prior to the Revolution, the clerics had shown no interest in politically mobilizing the urban poor from the slums or from the informal settlements in the south. Only subsequently were they courted by the Islamists and the left-wing groups. In around 1980 at least a million Tehranians lived in the impoverished areas, and an estimated 400,000 in the informal settlements, which were regularly attacked and torn down by the city authorities.

The Revolution and the Iran–Iraq War precipitated a collapse in the urban structures. The upper echelons of society fled into exile, clearing the path for a new affluent class. Their rise was founded on the war, inflation, and internal migration which transformed many of Tehran’s residential areas. Within the informal settlements, it was the mosque associations and the Islamic NGOs which during the 1980s and 1990s evolved into important local institutions, providing cultural, social, and material services which the state either neglected or failed to provide due to corruption.Under Mohammad Reza, the construction sector had been dominated primarily by foreign and foreign-educated architects. The Revolution put an end to this, the Islamic Republic went into isolation, and the new theocratic regime rejected the urban-planning master plan as a legacy of secularism. Yet little was done to tackle the population  explosion. In the 1990s, money was finally invested in the infrastructure, prompting the launch of one of the largest urban-planning projects of this time, the Navab. Running along the north–south axis, this eight-lane city highway is flanked by monumental postmodern buildings which extend for five kilometers. Astonishingly narrow in width, it also conceals behind it Tehran’s historical cityscape.

Today some 15 million people live in the greater conurbation of Tehran, of whom seventy percent are below age thirty. High rents are forcing more and more residents from the center into informal settlements. The government’s housing-construction programs are only slowly coming on stream, and for the time being, are unable to arrest this trend. Migrants account for a mere fifteen percent of residents, most of whom arrived from other cities. When in the wake of the election fraud in 2009, the Green movement formed, a diverse range of social groups took to the streets together for the first time to demonstrate against the theocratic regime and for civil rights and freedom. Although these protests were brutally crushed in Iran, they served as a blueprint for the “Arab Spring” some two years later. In 2011 there were mass protests against the ruling regimes across the whole of the Middle East.