Arbaeen is the 40th day since the martyrdom anniversary of Imam Hussain, the grandson of the prophet Mohammad. To mark the event, Muslims every year travel on foot to Iraq’s city of Karbala that hosts the holy shrine of Imam Hussain. The walk is one of the largest pilgrimages in the Islamic world. Our correspondent Nasir Kazmi traveled from the Iraqi city of Najaf to Karbala to bring us the highlights of this spiritual walk.