Mecca is generally considered "the fountainhead and cradle of Islam".^[4][5] Mecca is revered in Islam as the birthplace of the Islamic prophet Muhammad. The Hira cave atop the Jabal al-Nur ("Mountain of Light"), just outside the city, is where Muslims believe the Quran was first revealed to Muhammad.^[6] Visiting Mecca for the Ḥajj is an obligation upon all able Muslims. The Great Mosque of Mecca, known as the Masjid al-Haram, is home to the Ka'bah, believed by Muslims to have been built by Abraham and Ishmael. It is Islam's holiest site and the direction of prayer (qibla) for all Muslims worldwide.^[7]