The annual Islamic pilgrimage draws millions of visitors each year, making it the largest yearly gathering of people in the world. Around 2.5 million Muslims are expected to attend this year's Hajj pilgrimage, which is highlighted by the Day of Arafah, one day prior to Eid al-Adha. Eid al-Adha is the holiest of the two Muslims holidays celebrated each year, it marks the yearly Muslim pilgrimage (Hajj) to visit Mecca, the holiest place in Islam.