The Kaaba is the center of the holiest place of worship in Islam, the Sacred Mosque of Mecca, Al Masjid Al-Haram in Saudi Arabia. Its name means, “the cube” in Arabic, as it is a cube-shaped stone structure built in the middle of the Sacred Mosque. Tradition holds that the Kaaba was built by the prophet Abraham as a landmark for the House of God. Before the time of Muhammad, Meccans who lost the religion of Abraham's monotheism, worshipped many idols, most notable of which were al-Lat, al-Uzza and Manat.
The Kaaba is the center of the circumambulations performed during the pilgrimage (hajj), and it is toward the Kaaba that Muslims face in their prayers (salat).
The Kaaba is 50 ft. high, the shorter walls are about 35 ft long, and the longest walls are 40 ft. long. It is covered by golden lettered and black silk cloth, known as the Kiswa, which is replaced yearly. It contains the Hajar el Aswad (the sacred "Black Stone"), which is presumed by most sources to be a meteorite remnant. The Black Stone is located at one of its outside corners. It has been used by the pilgrims as a landmark to count the number of cicumambulations. Some traditional Muslims in defiance of their religion, consider the stone holy and put emphasis on touching it and kissing it.
The actual structure of the Kaaba has been demolished and rebuilt several times in the course of its history. Around the Kaaba is a restricted area, haram, extending in some directions as far as 12 miles, into which only Muslims may enter.
Source: Submission; The Columbia Encyclopedia, Sixth Edition. 2001; Wikpedia