The Kaaba is a shaped building in Mecca, Saudi Arabian and is the most sacred site in Islam. The building predates Islam, and, according to Islamic tradition, the first building at the site was built by Ibrahim. The building has a mosque built around it, the Masjid al-Haram. All Muslims around the world face the Kaaba during prayers, no matter where they are.
One of the Five Pillars of Islam requires every Muslim to perform the Haji pilgrimage at least once in his or her lifetime if they are able to do so. Multiple parts of the Hajj require pilgrims to walk seven 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). However, the most dramatic times are during the Hajj, when about three million (officially) pilgrims simultaneously gather to circle the building on the same day.
The Black Stone is a significant feature of the Kaaba, believed by Muslims to be placed there by Ibrahim (Abraham) and Ismail (Ishmael), a stone from paradise sent by the angels to Ibrahim. Some Western historians, however, think that the Black Stone was related to the pre-Islamic pagan culture of Arabia. Islamic sources do not consider kissing the black stone to be idolatry. Located at the eastern corner of the Kaaba, it is about 30 cm (12 in) in diameter and surrounded by a silver frame. Although not strictly obligatory, pilgrims can kiss the Stone, as Muhammad is said to have done.
The following passage gives an insight to the significance of the Black Stone in Islam:
1) Narrated 'Abis bin Rabia: Umar came near the Black Stone and kissed it and said, "No doubt, I know that you are a stone and can neither benefit anyone nor harm anyone. Had I not seen God's Apostle kissing you, I would not have kissed you."
2) Large crowds can make kissing the Stone impossible, so as pilgrims walk round the Kaaba they point to the Stone on each pass.