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

Once a year, Muslims coming to Saudi Arabia unite in a series of religious rituals and acts of worship as they perform Hajj, one of the pillars of Islam. As they fulfill a religious obligation, they immerse themselves in what can be a profound spiritual experience of a lifetime and a chance to seek God's forgiveness and the erasure of past sins. For the pilgrims, Hajj is also seen as an opportunity to grow closer to God and to walk in the footsteps of prophets. Hajj unites Muslims of diverse races, ethnicities, languages and economic classes in performing rituals together.