Islam, to make a pilgrimage, or Hajj, to Mecca during the Islamic month of Dhu al-Hijjah, at least once in his or her lifetime. The Masjid al-Haram (the Grand Mosque) in Mecca is the location of the Kaaba, Islam's holiest site, and the Masjid al-Nabawi (the Prophet's Mosque) in Medina is the location of Muhammad's tomb; as a result, from the 7th century, Mecca and Medina became pilgrimage destinations for large numbers of Muslims from across the Muslim world. Umayyad and Abbasid periods After the fall of the Umayyad empire in 750 CE, most of what was to become Saudi Arabia reverted to traditional tribal rule soon after the initial Muslim conquests, and remained a shifting patchwork of tribes and tribal emirates and confederations of varying durability. Muawiyah I, the first Umayyad caliph, took an interest in his native Mecca, erecting buildings and digging wells. Under his Marwanid successors, Mecca became the abode of poets and musicians. Even then, Medina eclipsed Mecca in importance for much of the Umayyad period, as it was home to the new Muslim aristocracy. Under Yazid I, the revolt of Abd Allah bin al-Zubair brought Syrian troops to Mecca. An accident led to a fire that destroyed the Kaaba, which was later rebuilt by Ibn al-Zubair. In 747, a Kharidjit rebel from Yemen seized Mecca unopposed, but he was soon defeated by Marwan II. In 750, Mecca, along with the rest of the caliphate, passed to the Abbasids. Sharifate of Mecca From the 10th century (and, in fact, until the 20th century) the Hashemite Sharifs of Mecca maintained a state in the most developed part of the region, the Hejaz. Their domain originally comprised only the holy cities of Mecca and Medina but in the 13th century, it was extended to include the rest of the Hejaz. Although the Sharifs exercised at most times independent authority in the Hejaz, they were usually subject to the suzerainty of one of the major Islamic empires of the time. In the Middle Ages, these included the Abbasids of Baghdad, and the Fatimids, Ayyubids, and Mamluks of Egypt. Ottoman era Beginning with Selim I's acquisition of Medina and Mecca in 1517, the Ottomans, in the 16th century, added to their empire the Hejaz and Asir regions along the Red Sea and the al-Hasa region on the Persian Gulf coast, these being the most populous parts of what was to