Faithful gather around for key ritual of the Haj

(Hassan Ammar/AP)

Tens of thousands of Muslim pilgrims move around the Kaaba, the black cube that sits within the Grand Mosque in Mecca, Saudi Arabia, during this year's Haj.

Pilgrims undertaking the Haj are required to walk seven times around the Kaaba in an anti-clockwise direction. The annual pilgrimage draws 2.5 million visitors each year, making it the largest yearly gathering of people in the world.