The prophet Mohammed's birthplace is Islam's spiritual center and is strictly off-limits to non-Muslims. The pillars of Islam state that all Muslims with the means must undertake Hajj, a pilgrimage to Mecca, once in their lifetime. Those who visit the holy city are rewarded not just by proximity to landmarks and religious sites crucial to the religion, such as the Masjid Al Haram (Holy Mosque), the Mountain of Light, the Black Stone, and the Well of Zamzam, but with the forgiveness of all their sins.