Al-Aqsa Mosque is a mosque located in the Old City of Jerusalem. It is considered the third holiest site in Islam. The covered mosque building was originally a small prayer house erected by Umar, the second caliph of the Rashidun Caliphate, but was rebuilt and expanded by the Umayyad caliph Abd al-Malik and finished by his son al-Walid in 705 AD. The mosque was completely destroyed by an earthquake in 746 AD and rebuilt by the Abbasid caliph al-Mansur in 754 AD. It was rebuilt again in 780 AD. Another earthquake destroyed most of al-Aqsa in 1033 AD, but two years later the Fatimid caliph Ali az-Zahir built another mosque whose outline is preserved in the current structure. The mosque was inscribed as a UNESCO World Heritage Site in 1981 as part of Old City of Jerusalem and its Walls.