Muslim worshipers pray at the Kaaba, Islam’s holiest shrine, at the Grand Mosque in Saudi Arabia’s holy city of Mecca, June 23, during the last Friday of the holy month of Ramadan.

The Kaaba sits at the center of the sacred al-Haram Mosque in Saudi Arabia. It plays an essential role in the rite of the hajj, the pilgrimage that Muslims make to Mecca, which begins today.

Though technically outside the Kaaba’s structure, it is considered a part of it. Pilgrims often pray within this area, which is believed to be the burial place of Prophet Ismail and his mother ...