Millions gather in Karbala, Iraq, for the Shia Arba'in pilgrimage

Millions of pilgrims from around the world descended on Karbala, Iraq, in August for the Shia Muslim Arba'in pilgrimage, one of the world's largest annual religious gatherings. Many Iraqi and Iranian pilgrims walked hundreds of miles in extreme heat to reach the holy site. The atmosphere near the shrines was described as almost festive despite the demanding journey.