Mecca, located in present-day Saudi Arabia, is the holiest city in Islam. It is the birthplace of the Prophet Muhammad and the site of the Kaaba, a cube-shaped structure draped in black cloth, which Muslims worldwide face during prayer. Every year, millions of Muslims undertake the Hajj, a pilgrimage to Mecca, fulfilling one of the five pillars of Islam. Non-Muslims are generally prohibited from entering the city. Mecca's significance is deeply rooted in Islamic history and tradition, making it the spiritual center of the Muslim world.