Millions of Muslims have gathered in Mecca, marking the beginning of the five-day Hajj pilgrimage—the world's largest annual religious gathering. It is year 1446 in the Islamic calendar. Pilgrims are expected to retrace the steps of the Prophet Muhammad,

Here is a look at the hajj, one of the largest mass gatherings in the world, which starts in Saudi Arabia on Wednesday.

Millions of Muslims from all over the world have converged on Mecca in Saudi Arabia to partake in Islam's annual Hajj pilgrimage.