The Arba'een Pilgrimage, or the Arba'een Walk or Karbala Walk, is the world's largest annual public gathering. It is held at Karbala, Iraq at the end of the 40-day mourning period following Ashura, the religious ritual for the commemoration of martyrdom of the grandson of the Islamic prophet Muhammad and the third Shia Muslim Imam, Husayn ibn Ali's in 61 AH (680 AD). He is believed to transcend all cultural boundaries and be a symbol of universal freedom, compassion and social justice. Anticipating Arbaʽeen, or the fortieth day of the martyrdom, the pilgrims make their journey to Karbala on foot, where Husayn and his companions were betrayed by the very people who invited him to Kufa, Iraq, and then subsequently martyred and beheaded by the army of Ubayd Allah ibn Ziyad in the Battle of Ka