(2 of 4) In 1889, a view of the Kaaba inside the Masjid al-Haram, in Mecca. #

(3 of 4) On September 7, 1954, Muslims visit the Kaaba, during a pilgrimage to Mecca. #

(4 of 4) An aerial view of Mecca and the the Masjid al-Haram in 1988. #

The Masjid al-Haram, as it stands today. Muslim pilgrims circle the Kaaba as they pray inside and outside the Grand mosque in Mecca, on October 22, 2012. #

Clouds gather over the Saudi holy city of Mecca as seen from the top of Mount Noor, on the outskirts of Mecca, on October 21, 2012. #

Muslim pilgrims pray on a rocky hill called the Mount Mercy on the Plain of Arafat near Mecca, on October 25, 2012. #

Muslim pilgrims climb Mount Mercy on the Plain of Arafat, on October 25, 2012. #

Muslim pilgrims atop Mount Mercy, during the peak of the annual Halj pilgrimage, on October 25, 2012. #

Muslim pilgrims pray at the top of Mount Noor, on October 21, 2012. #

Pilgrims pray on Mount Mercy, near Mecca, Saudi Arabia, on October 25, 2012. #

Lightning strikes, seen from the top of Mount Noor during the 2012 Hajj, on October 21, 2012. #

The Grand Mosque at night, viewed from the top of Mount Noor, on October 21, 2012. #

Muslim pilgrims circle the Kaaba and pray at the Grand mosque in Mecca, on October 18, 2012. #

Pilgrims circle the Kaaba inside the Grand mosque in Mecca, on October 22, 2012. #

Muslim pilgrims pray in unison inside the Grand mosque, on October 22, 2012. #

Pilgrims in motion near the Kaaba inside the Grand mosque, on October 23, 2012. #

Pilgrims at prayer inside the Grand mosque, on October 22, 2012. #

A whirl of pilgrims circle the Kaaba and pray in front of Station of Ibrahim "Maqam Ibrahim" at the Grand mosque during the annual Hajj, on October 23, 2012. #

Hajj pilgrims circle the Kaaba and pray at the Grand mosque, on October 23, 2012. #

Muslim pilgrims touch the the Yamani corner of the Kaaba, as they pass by it inside the Grand mosque, on October 23, 2012. #

A boy stands beside his father, as Muslim pilgrims pray in the Grand mosque in Mecca, on October 23, 2012. #

Pilgrims pass by, and reach out to touch the Kaaba in the holy city of Mecca, on Tuesday, October 23, 2012. #

Muslims circle the Kaaba, on October 23, 2012. #

Pilgrims head towards Mount Mercy at the peak of the annual Hajj, on October 25, 2012. #

Muslim faithful pray outside Namira mosque in Arafat, near Mecca, on October 25, 2012. #

Thousands of pilgrims perform the noon prayer in the plain of Arafat, on October 25, 2012. #

The four-faced Mecca Clock Tower, seen from the top of Mount Noor, in Mecca, during the Hajj on October 21, 2012. #