Covering a huge area of 99 acres (356,800 sq m) and equipped with outdoor and indoor praying spaces that can accommodate around four million people, Al-Haram Mosque or the Great Mosque that surrounds the Kaaba in Mecca, is regarded as the holiest place in Islam. At the epicenter of the mosque is the Holy Kaaba, covered in black and gold cloth, that predates the Prophet Muhammad's lifetime, around which Muslims can be found circumnavigating night and day, known as Tawaf, Al-Haram Mosque also contains many other significant sites which include, among others, the Black Stone, Maqam Ibrahim, and the Zamzam Well.

It is believed by many that Kaaba was a sanctuary that existed in pre-Islamic days.

The Muslims believe that Abraham, known as Ibrahim in the Islamic tradition, and his son Ismail, constructed the Kaaba, a simple rectangular structure. After the completion of the structure, the angel Gabriel brought to him the Black Stone, a celestial stone, which is believed to be the only remnant of the original structure made by Abraham. However, it is also believed that the Black Stone had fallen from Heaven on the nearby hill Abu Qubays, which Gabriel collected for Abraham.

Apart from the Black Stone, the pre-Islamic Kaaba also housed several statues of the pagan gods. However, after his victorious return to Mecca in 603 AD, Muhammad, along with his cousin Ali ibn Ali Talib, reportedly broke all the idols in and around the Kaaba to end the polytheistic use of the Kaaba and began the monotheistic rule over it and its sanctuary. But as the Black Stone believed to be gifted to Ibrahim by the angel Gabriel, it remained as it was and is revered by Muslims.

Throughout its history, the Kaaba has been extended and modified extensively. The second caliph, Umar Bin Al Khattab, who ruled between 634 and 644 AD, built the foundations of the mosque around the Kaaba, along with a structure to accommodate the growing number of pilgrims each year. When Uthman ibn Affan succeeded him as the second-oldest to rule as Caliph between 644 and 656, he built the colonnades around the open plaza where the Kaaba stands and incorporated other important monuments into the sanctuary.

The Kaaba was set on fire in 683, during the civil war between the caliph Abd al-Malik and Ibn Zubayr, and the Black Stone was reportedly broken into three pieces. Eventually, Ibn Zubayr, who controlled Mecca during that time, reassembled it with silver. Following Ibrahim’s original dimensions, he also rebuilt the Kaaba in wood and stone and paved the space around the Kaaba. Later, after regaining control of Mecca, Abd al-Malik restored the part of the building that Muhammad is thought to have designed.

But there is no documentary evidence to confirm those expansions and renovations. Nevertheless, before the first major renovation that took place in 692, when Abd-Malik ibn Marwan, the fifth Umayyad caliph, raised the outer walls of the mosque and added decorations to the ceiling, the mosque was a humble open area with the Kaaba at the centre. Subsequently, during the reign of the Umayyad caliph al-Walid between 705 and 715 AD, the mosque that encloses the Kaaba was decorated with mosaics, the old wooden columns of the mosque were replaced with marble columns, and the wings of the prayer hall were extended on both sides along with the addition of a minaret.

In 1570, Sultan Selim II of the Ottoman Empire thoroughly renovated the mosque, along with the complex, which resulted in the replacement of the flat roof of the mosque with domes, internally decorated with calligraphy, and the placement of new support columns. However, the Kaaba and the surrounding mosque were entirely rebuilt in 1629, during the reign of Sultan Murad IV, as heavy rains and flash floods in 1621 and 1629 played havoc, and the walls of the Kaaba and the mosque suffered extensive damage.

During the Saudi era, the mosque and the complex were expanded, renovated, and refurnish several times. The Al-Haram Mosque, which stands today, is composed of a large open space with colonnades on four sides and decorated with seven minarets, the largest number of any mosque in the world. Surrounded by many holy buildings and monuments, the fifteen metres (around 49 feet) tall Kaaba sits at the centre of a huge plaza. Its door, made of solid gold, was added in 1982. At one time, the large cloth that covers the Kaaba, called Kiswa, used to be sent from Egypt with the hajj caravan, but today it is made in Saudi Arabia

The Al-Haram Mosque is a site of pilgrimage in the Hajj, an annual Islamic pilgrimage to Mecca in Saudi Arabia, the holiest city for Muslims. However, only Muslims can visit the holy cities of Mecca and Medina today.