What's Hajj, the Islamic pilgrimage, and why is it significant for Muslims?

Once a year, Muslim pilgrims flowing into Saudi Arabia unite in a series of religious rituals and acts of worship as they perform the Hajj, one of the pillars of Islam. As they fulfill a religious obligation, they immerse themselves in what can be a spiritual experience of a lifetime for them and a chance to seek God's forgiveness and the erasure of past sins.

Here's a look at the pilgrimage and its significance to Muslims.

Hajj is the annual Islamic pilgrimage to Mecca in Saudi Arabia that is required once in a lifetime of every Muslim who can afford it and is physically able to make it. Some Muslims make the journey more than once.