The Great Hosseinieh Mosque in Zanjan dates back to the Safavid period because this time was associated with the officialization of the Shiite religion by Shah Ismail Safavid in Iran. The mourning at 8th Muharram or the night of Tasu'a is the most famous and crowded program in Hosseinieh. It is held every year with hundreds of thousands of people in the name and memory of Hazrat Abolfazl Al-Abbas. This category of mourning is mentioned as the largest gathering of mourners for Hazrat Seyyed Al-Shohada (AS) in Iran, so that the Great Husseinieh of Zanjan is called the capital of Hosseini mourning. The number of people gathered in Hosseinieh Azam is estimated at 500,000 which is one of the largest religious communities in Iran.
The eighth day of Muharram is known in the calendar of events in Zanjan province as Abul-Fazl Day and Abbas Day. On this day, thousands of victims are slaughtered in the direction of the Hosseinieh or donated to the mosque. This ceremony was registered as the tenth spiritual heritage of Iran.
This hosseinieh is the second altar in the Islamic world after the Mena altar in Mecca in terms of the number of animals that are sacrificed in the path of Hosseini mourners, on the eighth day of Muharram.
The Great Hosseinieh of Zanjan is one of the most influential cultural and religious centers of Zanjan. This complex has more than twelve thousand square meters, and there are numerous cultural, religious, medical, and service facilities and spaces such as a library, Dar al-Shifa, Gharz al-Hasna fund, and so on.