The annual hajj pilgrimage to Mecca in Saudi Arabia began on Sunday, with more than 2 million Muslims from around the world expected to arrive to circle the black Kaaba rock.

The hajj — very similar to the Hebrew word chag, or “holiday” — is a pilgrimage required of all healthy Muslims at least once in their lives.

Prior to Mecca, many Muslims stop in Medina — the place where Muhammad is buried and built his first mosque, according to Islamic teachings. Following the circling around the 43-foot-tall granite Kaaba stone, they walk between two hills they say was traveled by Hagar, the matriarch they assert was the true wife of the Jewish patriarch Abraham.

They then move on to Mount Arafat, where Muhammad is said to have delivered his last sermon, and on to an area called Muzdalifa to pick up rocks, finally ending up in Mina, where they throw rocks at pillars meant to represent the Devil.

Male pilgrims end the ritual by shaving all their hair, and women cut off a lock of hair to symbolize their renewal. The Eid al-Adha holiday, which is celebrated in Muslim communities around the world, involves the slaughtering of sheep and cows, with distribution of meat to the indigent.