The Ka'ba is the place of worship which God commanded Abraham and Ishmael to build over four thousand years ago. The building was constructed of stone on what many believe was the original site of a sanctuary established by Adam. God commanded Abraham to summon all mankind to visit this place, and when pilgrims go there today they say 'At Thy service, O Lord', in response to Abraham's summons.
The building has a mosque built around it, the Masjid al-Haram.
Every capable Muslim to perform the Hajj pilgrimage at least once in their lifetime. Multiple parts of the Hajj require pilgrims to walk several times around the Kaaba in a counter-clockwise direction (as viewed from above). This circumambulation, the Tawaf, is also performed by pilgrims during the Umrah (lesser pilgrimage).
The Kaaba is a large masonry structure roughly the shape of a cube. It is made of granite from the hills near Mecca, and stands upon a 25 cm (10 in) marble base, which projects outwards about 35 cm (1 ft).It is approximately 13.10 m (42.98 ft) high, with sides measuring 11.03 m (36.19 ft) by 12.86 m (42.19 ft). The four corners of the Kaaba roughly face the four cardinal directions of the compass.In the eastern corner of the Kaaba is the Ruknu l-Aswad "Black Stone" or al-Ħajaru l-Aswad, possibly a meteorite remnant; at the northern corner is the Ruknu l-ˤĪrāqī "The Iraqi corner". The western corner is the Ruknu sh-Shāmī "the Levantine corner" and the southern is Ruknu l-Yamanī "the Yemeni corner".The Kaaba is covered by a black silk and gold curtain known as the kiswah, which is replaced yearly. About two-thirds of the way up runs a band of gold-embroidered calligraphy with Qur'anic text, including the Islamic declaration of faith, the Shahadah.
Further readings reference on Kaabah can be found at http://www.islamonline.net/English/hajj/2002/01/stories/article2.shtml#11
