The Kaaba or Ka'aba (Arabic: الكعبة al-Kaʿbah IPA: [ælˈkæʕbɐ], "The Cube"), is a cuboid building at the centre of Islam's most sacred mosque, Al-Masjid al-Haram, in Mecca, Saudi Arabia. It is the most sacred point within this most sacred mosque, making it the most sacred location in Islam. Wherever they are in the world, Muslims are expected to face the Kaaba – i.e. when outside Mecca, to face toward Mecca – when performing salat (prayers).
Al-Masjid al-Haram was built around the Kaaba. From any point in the world, the direction facing the Kaaba is called the qibla.
One of the Five Pillars of Islam requires every Muslim, who is able to do so, to perform the hajj pilgrimage at least once in their lifetime. Multiple parts of the hajj require pilgrims to make tawaf, the circumambulation seven times around the Kaaba in a counter-clockwise direction. Tawaf is also performed by pilgrims during the umrah (lesser pilgrimage). However, the most interesting times are during the hajj, when millions of pilgrims gather to circle the building on the same day. In 2013, the number of pilgrims coming from outside the Kingdom of Saudi Arabia to perform hajj was officially reported as 1,379,531. In 2014, Saudi Arabia reported having completed Hajj permits for 1,389,053 international pilgrims and 63,375 for residents. (Wikipedia)
A picture of people performing Tawaf (circumambulating) the Kaaba.
Labeled elements are as follows: 1 - The Black Stone; 2 - Door of the Kaaba; 3. Gutter to remove rainwater; 4 - Base of the Kaaba; 5 - Al-Hatim; 6 - Al-Multazam (the wall between the door of the Kaaba and Black Stone); 7 - The Station of Ibrahim; 8 - Corner of the Black Stone; 9 - Corner of Yemen; 10 - Corner of Syria; 11 - Corner of Iraq; 12 - Kiswa (black veil covering the Kaaba); 13 - marble band of marking the beginning and end of rounds; 14 - The Station of Gabriel.