Mecca, which is in modern-day Saudi Arabia, is the holiest city in Islam. It was the birthplace of the Prophet Muhammad, the founder of Islam, and the place where the first revelation of the Quran, Islam's holy book, occurred. From the time of Muhammad onwards, Mecca has had great cultural and religious significance in the lives of Muslims the world over.
It is renowned as a holy place and is visited by millions of Muslims each year as part of the Hajj, or pilgrimage. During the Hajj, pilgrims circle round the Kaaba—the holiest site in Islam—a giant cuboid structure at the heart of The Sacred Mosque. According to the Quran, it was the first Islamic house of worship, built by Ibrahim and Ishmael on the orders of Allah. The Kaaba is so important to Muslims that they face in its direction whenever they pray.