The Prophet's Mosque is the second mosque built by the Islamic prophet Muhammad in Medina, after the Quba Mosque, as well as the second largest mosque and holiest site in Islam, after the Masjid al-Haram in Mecca, in the Saudi region of the Hejaz. The mosque is located at the heart of Medina, and is a major site of pilgrimage that falls under the purview of the Custodian of the Two Holy Mosques. Muhammad himself was involved in the construction of the mosque.