Before Reza Shah Pahlavi ordered its construction in the 1920s, the route was nothing more than a dirt track connecting the palaces of northern Tehran to the Marble Palace downtown. Reza Shah began buying land along the corridor, including property that had belonged to a daughter of Naser al-Din Shah Qajar, and commissioned a proper avenue to connect his royal residences. He named it Pahlavi Street. Plane trees were planted, a stream was built alongside the road, and in 1931 it became one of the first streets in Tehran to be asphalted. In 1938, rose bushes went in between the saplings, and wells were dug in Zafaraniyeh to irrigate them. Until 1940, the street was restricted to government officials. Only when Allied forces arrived in wartime Iran did it open to the public.

The street has been renamed twice, and each name tells a political story. Reza Shah called it Pahlavi Street, stamping his dynasty's identity onto Tehran's geography. After the 1979 Revolution, it was briefly renamed Mossadegh Street, honoring the nationalist prime minister who had been overthrown in a 1953 coup. That name did not stick. The revolutionary government settled on Valiasr -- a title for the 12th Shia Imam, the Mahdi -- transforming the boulevard from a monument to secular monarchy into a reference to messianic faith. Tehranis use all three names interchangeably, depending on their generation and politics. The street absorbs contradictions the way its plane trees once absorbed carbon dioxide.

The plane trees were always the soul of Valiasr. Oriental planes can live for centuries, and the oldest specimens on the street date to the original 1920s plantings. But decades of urban assault have devastated them. Natural waterways that once fed the roots have been paved over. High-rise buildings block sunlight. Soil contamination and air pollution weaken what remains. In July 2022, a property owner deliberately poisoned 13 trees to improve the visibility of a building's facade -- and was fined $3.8 million for it. By 2023, authorities announced that 179 trees would need to be cut down and replaced. The decline from 24,000 to roughly 8,000 trees over seven decades is not just an environmental statistic. It is visible from the air: where the canopy once formed an unbroken green ribbon dividing Tehran east from west, gaps now interrupt the line like missing teeth.

Walking Valiasr from south to north is walking through Tehran's entire social geography. The southern end, near the railway station at 1,117 meters elevation, is working-class and dense, close to the Grand Bazaar. Moving north, the street passes the Tehran City Theatre, Mellat Park, and the cultural district, then climbs into the wealthier neighborhoods where luxury shops selling Rolex watches and Benetton clothing line the avenue. By the time you reach Tajrish Square at 1,612 meters elevation, the air is cooler and the money is older. The street never sleeps -- traffic clogs it at all hours, kiosks sell fresh juice and newspapers past midnight, and the sidewalk cafes fill every evening. For all the changes its trees have suffered, Valiasr remains the artery through which Tehran's daily life pumps.