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 (14 in). It is approximately 13.1 m (43 ft) high, with sides measuring 11.03 m (36.2 ft) by 12.86 m (42.2 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 "the Black Corner" the Black Stone", possibly a meteorite remnant; at the northern corner is "the Iraqi corner". The western corner is "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 Shahada. In modern times, entry to the Kaaba's interior is generally not permitted except for certain rare occasions and for a limited number of guests. The entrance is a door set 2 m (7 ft) above the ground on the north-eastern wall of the Kaaba.There is a wooden staircase on wheels, usually stored in the mosque between the arch-shaped gate of Banū Shaybah and the well of Zamzam. Inside the Kaaba, there is a marble and limestone floor. The interior walls are clad with marble halfway to the roof tablets with Qur'anic inscriptions are inset in the marble. The top part of the walls are covered with a green cloth decorated with gold embroidered Qur'anic verses. Caretakers perfume the marble cladding with scented oil, the same oil used to anoint the Black Stone outside. There is also a semi-circular wall opposite, but unconnected to, the north-west wall of the Kaaba known as the hatīm. This is 90 cm (35 in) in height and 1.5 m (4.9 ft) in width, and is composed of white marble. At one time the space lying between the hatīm and the Kaaba belonged to the Kaaba itself, and for this reason it is not entered during the tawaf (ritual circumambulation). Some believe that the graves of Abu Simbel, prophet Ishmael and his mother Hagar[2] are located in this space. Muslims throughout the world face the Kaaba during prayers, which occur five times a day. For most places around the world, coordinates for Mecca suffice. Worshippers in the Sacred Mosque pray in concentric circles around the Kaaba.

The Black Stone is a significant feature of the Kaaba, believed by Muslims to date back to the time of Adam and Eve. Located on the eastern corner of the Kaaba, it is about 30 cm (12 in) in diameter and surrounded by a silver frame. All Hajj pilgrims must attempt to kiss the Stone as Muhammad once did. If they cannot then a flying kiss would be sufficient Because of the large crowds, this is not always possible, and so as pilgrims walk around the Kaaba, they are to point to the Stone on each circuit.

As little is known of the history of the Kaaba, there are various opinions regarding it's formation and significance. The early Arabian population consisted primarily of warring nomadic tribes. When they did converge peacefully, it was usually under the protection of religious practices. Writing in the Encyclopedia of Islam, Wensinck identifies Mecca with a place called Macoraba mentioned by Ptolemy. His text is believed to date from the second century AD, before the rise of Islam, and described it as a foundation in southern Arabia, built around a sanctuary. The area probably did not start becoming an area of religious pilgrimage until around the year AD 500. It was around then that the Quraysh tribe (into which Muhammad was later born) took control of it, and made an agreement with the local Kinana Bedouins for control. The sanctuary itself, located in a barren valley surrounded by mountains, was probably built at the location of the water source today known as the Zamzam Well, an area of considerable religious significance. Imoti contends that there were multiple such "Kaaba" sanctuaries in Arabia at one time, but this is the only one built of stone. The others also allegedly had counterparts to the Black Stone. There was a "red stone", the deity of the south Arabian city of Ghaiman, and the "white stone" in the Kaaba of al-Abalat (near the city of Tabala, south of Mecca). Grunebaum in Classical Islam points out that the experience of divinity of that time period was often associated with stone fetishes, mountains, special rock formations, or "trees of strange growth." According to Karen Armstrong, in her book Islam: A Short History, the Kaaba was dedicated to Hubal, a Nabatean deity, and contained 360 idols which either represented the days of the year, or were effigies of the Arabian pantheon. Once a year, tribes from all around the Arabian peninsula, be they Christian or pagan,would converge on Mecca to perform the Hajj.

The Kaaba has been repaired and reconstructed many times since Muhammad's day. Abd-Allah ibn al-Zubayr, an early Muslim who ruled Mecca for many years between the death of ʿAli and the consolidation of Ummayad power, is said to have demolished the old Kaaba and rebuilt it to include the hatīm, a semi-circular wall now outside the Kaaba. He did so on the basis of a tradition (found in several hadith collections) that the hatīm was a remnant of the foundations of the Abrahamic Kaaba, and that Muhammad himself had wished to rebuild so as to include it. This structure was destroyed (or partially destroyed) in 683 during the war between al-Zubayr and Umayyad forces commanded by Al-Hajjaj bin Yousef. Al-Hajjaj used stone-throwing catapults against the Meccans. The Ummayads under Abdu l-Malik ibn Marwan finally reunited all the former Islamic possessions and ended the long civil war. In 693 he had the remnants of al-Zubayr's Kaaba razed, and rebuilt on the foundations set by the Quraysh. The Kaaba returned to the cube shape it had taken during Muhammad's lifetime. During the Hajj of 930, the Qarmatians attacked Mecca, defiled the Zamzam Well with the bodies of pilgrims and stole the Black Stone, removing it to the oasis region of Eastern Arabia known as al-Aḥsā, where it remained until the Abbasids ransomed it back in 952 CE. Apart from repair work, the basic shape and structure of the Kaaba have not changed since then. The Kaaba is depicted on the reverse of 500 Saudi Riyal, and the Iranian 2000 rials banknotes.