The Ka'aba is an ancient Arabic shrine located in Mecca. It is thought to be the holiest place on earth for the people of Islam, and when people pray toward Mecca, they specifically pray toward the direction of the Ka'aba. Thus Arabs in Mecca north of the shrine would direct their prayers south.
Before Islam, the Ka'aba was an important shrine, and perhaps a source of pilgrimage for many in the Arabic world. Since people often worshiped local gods, the inside of the shrine usually had statues or idols designated to their specific gods. When Muhammad began to preach, one of his teachings was that the Ka'aba was originally built by Abraham and his son Ishmael, the son to which Islam claims descendancy.
Since the Ka'aba was built by the prophet Abraham, also called Ibrahim in Islam, it was meant to be a place for Islamic worship of Allah only, according to Muslim doctrine. When Muhammad first began to preach in Mecca, he advocated for removal of the other idols in the shrine, an unpopular theme. The idols were not thrown out until Muhammad returned to Mecca after exile in Medina.
Of particular interest in the Ka'aba, to certain Islamic sects, is a black cornerstone surrounded by silver. To some Muslims, the stone is merely a point of reference in counting the ritual circling of the Ka'aba during the Hajj. Others believe the stone was discovered by Abraham and Ishmael, and specifically placed there. It is known that many prior to the advent of Islam worshiped the stone. Some Islamic sects still revere it, as having been important to Muhammad and perhaps once kissed by him.
The Ka'aba is nearly cube like in shape, and the name derives from the Arabic word for cube muka'ab. Excluding the black stone, the shrine is made from granite and stands about 49 feet (14.93 m) high. Each corner corresponds with the compass directions of north, south, east and west. There is evidence the Ka'aba has been rebuilt numerous times. Some believe it may have been rebuilt when Muhammad was a boy. The black stone was stolen in 930 CE, and was not returned until 952 CE.
Today, the Ka'aba is typically covered with a black silk cloth embroidered with gold thread. Each year the cloth is replaced. Two times a year the shrine undergoes an official cleaning. One of these cleanings occurs just before the Hajj, and the other occurs before Ramadan.