The Great Mosque of Mecca, also known as Al-Masjid al-Haram, is the holiest mosque in Islam, located in the city of Mecca, Saudi Arabia. It is the largest mosque in the world, covering an area of 356,800 square meters, and is capable of accommodating up to two million worshippers during the Hajj pilgrimage.
At the heart of Al-Masjid al-Haram lies the Kaaba, a cube-shaped structure draped in black silk and gold, which is considered the "House of God" by Muslims. Muslims around the world face the Kaaba during their daily prayers. The mosque also houses the Zamzam well, believed to possess healing properties, and the Maqam Ibrahim, a revered place of prayer.
Every year, millions of Muslims travel to Mecca to perform the Hajj, one of the Five Pillars of Islam, making the Great Mosque of Mecca the most visited religious site in the world.
Source: Wikipedia