The city of Makkah itself is only accessible to Muslims. Each year, it bears witness to the Hajj pilgrimage, a religious duty that must be performed by every able Muslim at least once in their lifetime, and which draws millions each year. Holy sites in the city include the sacred Ka’aba, located in the heart of the Masjid al-Haram, or Grand Mosque, while the circling mountains house the historic Cave of Thawr, where the Prophet sought refuge from the Quraysh tribe, and the revered Jabal Rahmah, where he delivered his last sermon.