The long procession in a cold and cloudy day proceeded to the holy shrine of Abdol Azim al-Hasani (AS) in Rey, south of Tehran.
Pedestrians, many of them families, walked long distances from different parts of Tehran to the sacred shrine.
Arbaeen is a national holiday in Iran. It marks the 40th day after Ashura, the martyrdom anniversary of Imam Hussein (AS), the grandson of Prophet Mohammad (PBUH), in 680 AD.
Each year, millions of pilgrims, mainly from Iraq and Iran, travel long routes on foot to Karbala, where the holy shrine of Imam Hussein (AS) is located.