Ka'ba, or Ka'bah, (Arabic, cube) is the building, deeply revered by Muslims, in the center of the great mosque at Mecca, in the eastern corner of which, about five feet from the ground, is embedded the Black Stone. The Ka'ba, about 35 feet by 40 feet and 50 feet high, is called the house of Allah, and is the focus of the daily salat of Muslims throughout the world, and of the annual hajj (pilgrimage). According to Islamic tradition, the Ka'ba was originally built by Adam, and then rebuilt by Ibrahim and his son as a place for pilgrimage (Qur'an 2. 123; 22. 126). By the time of Muhammad it had become a center where pagan ceremonies were held. After the conquest of Mecca in 650 AD, Muhammad cleansed the Ka'ba, throwing out all the idols of which there was said to be over 300. The Ka'ba is covered with a huge cloth (kiswa) and is only entered once a year at the time of hajj. It is believed to have been built directly under an equivalent Ka'ba in heaven, and it is the exact point to which Muslims turn in their prayers.