The Haram is the holiest mosque in the world and the primary destination of the Hajj pilgrimage. The mosque complex covers an area of 356,800 square meters and can accommodate up to 820,000 worshippers during the Hajj. The Holy Mosque is the only mosque that has no qibla direction, since Muslims pray facing the Ka'aba in the central courtyard. was built in the 7th century and has been modified, rebuilt, and expanded on a regular basis ever since. Major expansions took place in the 1980s and further work is going on today. The beginnings of the Holy Mosque were established under Caliph Omar Ibn al-Khattab (634-644).