Al-Masjid al-Haram, the most sacred mosque in Islam, is built around the Kaaba. Muslims are expected to face the Kaaba during prayers, no matter where they are. From any given point in the world, the direction facing the Kaaba is called the Qibla.
One of the Five Pillars of Islam requires every Muslim to perform the Hajj pilgrimage at least once in his or her lifetime if able to do so. Multiple parts of the Hajj require pilgrims to make Tawaf, the circumambulation seven times around the Kaaba in a counter-clockwise direction. This circumambulation is also performed by pilgrims during the Umrah (lesser pilgrimage). However, the most dramatic times are during the Hajj, when millions of pilgrims gather to circle the building on the same day. In 2013, the number of pilgrims coming from outside the kingdom of Saudi Arabia to perform Hajj was officially reported as 1,100,544.