Mecca is regarded as the holiest city in Islam and millions of Muslims flock to its mosques every year for worship and devotion. It is one of the Five Pillars of Islam to go on a pilgrimage to Mecca, Hajj, at least once in lifetime, and it is greatly encouraged to make another one, called Umrah. Mecca's importance is tied to the life and message of Prophet Muhammad, because it was here that the Prophet was born, and it was also here that God sent him the first revelation of the Quran through the archangel Gabriel. Since the Prophet's time Mecca has been at the centre of the Muslim world, for it is facing towards it that all Muslims pray every day. In recent years, however, the city has suffered a contradictory policy (imposed by the Saudi government) of destroying historical sites, such as the birthplace of Prophet Muhammad, for fear that people would worship him instead of God and, most importantly, to make room for hotels and shopping malls. Such was the fate of the house of Abu Bakr, loyal companion of the Prophet, replaced by the Hilton Hotel. Mecca is a city of contradictions but it still retains enormous historical significance, even with the threat of bulldozers ready to raze old monuments to the ground for the sake of money and grandeur.