Imagine a road, eighty kilometres long, filled shoulder to shoulder with people walking in the same direction. Old men, children on shoulders, wheelchairs, whole families. Along the roadside, strangers pull you in to feed you, pour you tea, and offer you a place to sleep — and they will not take a penny. This happens every year. Up to twenty million people take part. It is very likely the largest gathering of human beings on earth, and there is a good chance you have never heard of it.
It is called Arbaeen. If Islam, Shia Islam, and the events of Karbala are all new to you, this is the right place to begin — no prior knowledge assumed.
The one-sentence version
Arbaeen marks the fortieth day of mourning for Imam Hussain, the grandson of the Prophet Muhammad, who was killed in the year 680 CE for refusing to pledge allegiance to a tyrant. Every year, millions walk to his shrine in Karbala, in modern Iraq, to honour that stand.
Why walk?
People walk out of love, and out of remembrance. But you do not have to share the faith to feel the pull of the story: a man who chose to die on his feet rather than live on his knees, and a community that answers his memory not with anger, but with almost unimaginable generosity to strangers.
Where to go next
If your curiosity is stirred, read what Arbaeen is in more depth, meet the man millions walk for, or learn what actually happened at Karbala. There is no wrong door.