A pilgrimage to Mecca, known as the Hajj, is one of the Five Pillars of Sunni Islam and one of the ten Branches of Religion in Shi'a Islam, and thus obligatory for all Muslims with the physical and financial ability to make it. Over three million Muslims visit the city during the month of Dhu'l-Hijjah yearly. Visits outside this month are known as minor pilgrimages or Umrah, and while not compulsory are strongly encouraged. This is also the place where Muhammad was born.