The Hajj pilgrimage has officially started in Saudi Arabia. Some 2 million pilgrims are making their way from the holy city of Mecca on Monday to a tent camp on its outskirts for a day and night of prayer after circling the Kaaba, Islam's holiest site. One of the largest religious gatherings in the world has returned to full capacity this year for the first time since the onset of the coronavirus pandemic three years ago. The pilgrimage is one of the five pillars of Islam, and all Muslims are required to complete it at least once if they are physically and financially able.